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Summary

The current Diet of Japan was established in 1946 after the Second World War.  Under the post-war Constitution, the Diet was designated the highest organ of state power and the sole law-making organ of the state. 

The Diet consists of the House of Representatives and the House of Councillors.  Under Japan’s parliamentary cabinet system, the Prime Minister is the head of the Executive and elected from among Diet members.

Elections for the House of Representative are held every four years unless the House is dissolved.  Elections for half of the House of Councillors are held every three years.

Bills are generally submitted to the House of Representatives before the House of Councillors.  When both houses pass a bill, the bill is usually enacted into law.

I.  Background

The Imperial Diet, Japan’s first modern legislature, was established in 1890 under the 1889 Meiji Constitution, the first modern Constitution enacted in Japan.[1]  The Meiji Constitution gave the Emperor a broad range of strong powers.[2]  The Imperial Diet consisted of two houses: the House of Peers and the House of Representatives.  The former drew its members from the Imperial Family, the Peers (other nobles), people who paid high taxes, and others appointed by the Emperor.  The members of the latter were elected by limited franchise.[3]

The current Constitution was promulgated after the Second World War on November 3, 1946, and went into effect on May 3, 1947.[4]  The Imperial Diet enacted election laws that would comply with the new Constitution before it became effective.[5]  The 1945 amendment to the House of Representatives Members Election Act gave women voting rights for the first time.[6]  The first elections for both houses under the new Constitution were held on April 20 and 25, 1946.[7]  When the new Constitution took effect, the Imperial Diet was dissolved, and a new Diet was born.[8]  The first session of the National Diet was convened on May 20, 1947.[9]  

Under the new Constitution, the Emperor lost his powers and became a “symbol” of the nation.[10]  Instead, the Diet became the highest organ of state power.[11]

The Diet building is located in Nagatacho, Tokyo.  The Prime Minister’s residence is also located in Nagatacho.  Therefore, “Nagatacho” is often used to refer to Japan’s national government.[12]  The Diet building was constructed for the Imperial Diet, and it was first used in December 1936 (during the 70th Session of the Imperial Diet).  Japan’s House of Representatives is located on the left side of the building, and the House of Councillors is located on the right.[13]

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II.  Constitutional Status and Role

The Diet, which consists of the House of Representatives and House of Councillors, is the sole law-making organ of the State.[14]  Executive power is vested in the Cabinet.[15]  The Prime Minister represents the Cabinet, submits bills, reports on general national affairs and foreign relations to the Diet, and exercises control and supervision over various administrative entities.[16]  Under Japan’s parliamentary cabinet system,[17] the Prime Minister is designated from among the members of the Diet by a resolution of the Diet.[18]  The Cabinet is collectively responsible to the Diet in the exercise of executive power.[19]  If the House of Representatives passes a no-confidence resolution, either the House of Representatives must be dissolved or the Cabinet must resign en masse.[20]

The Diet’s powers, which are jointly exercised by its two houses, include the following:

  1. Enactment of laws,
  2. Decisions regarding the budget and other matters related to national finances,
  3. Decisions regarding approval for the conclusion of international treaties, [and]
  4. Designation of the Prime Minister . . . .[21]

In the rare event that the House of Councillors rejects a bill passed by the House of Representatives, the bill becomes law if passed again by the House of Representatives in a two-thirds vote.[22]

Chapter 1 of the Constitution contains provisions on the Emperor and his powers.  However, as the Constitution states only that the Emperor is “the symbol of the State,”[23] there is controversy over whether Japan can be considered a constitutional monarchy and whether the Emperor is the actual head of state.[24]

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III.  Structure and Composition

The Diet’s House of Representatives has 475 members, consisting of 295 members who are elected from single-seat districts and 180 proportionally elected from multiseat districts.  The House of Councillors has 242 members, consisting of 146 elected from multiseat prefectures and ninety-six proportionally elected from multiseat constituencies.[25]  The term of office for House of Representatives members is four years unless the House is dissolved within the term.[26]  The term of office for the House of Councillors is six years, with half of the members elected every three years.[27]  While citizens must be twenty-five years of age or older to run for office in the House of Representatives, the age requirement is thirty years of age or older for the House of Councillors.[28]   

Each house has a Chairman and a Vice-chairman,[29] who remain in their positions for the extent of their terms as House members.[30]  Chairmen are responsible for maintaining order in the house, managing meetings, supervising the administration of the house, and representing the house.[31]

The House of Representatives and the House of Councillors each have seventeen standing committees,[32] such as the Cabinet, Internal Affairs and Communications, Judicial Affairs, Foreign Affairs, and Financial Affairs committees.[33]  Each house can pass resolutions to establish special committees for a given Diet session whenever necessary.  Every Diet member serves on at least one standing committee during his or her term of office.[34]

The Liberal Democratic Party (LDP) has been Japan’s most popular political party and has governed Japan most of the time since 1955.[35]  The Democratic Party controlled the Diet and the Cabinet between 2009 and 2012, but had lost popularity by the end of 2011,[36] allowing the LDP to return to power in the 2012 election.[37]  Japan has several other parties,[38] including the Japanese Communist Party,[39] which has never held many seats in the Diet but still has a strong presence there.[40]  

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IV.  Elections

Elections for the House of Representatives are held every four years unless the House is dissolved.[41]  When it is dissolved, a general election is held within forty days from the date of dissolution.[42]  Elections for half of the House of Councillors are held every three years.[43]  There are no provisions in the Constitution or any Diet acts that impose term limits on Diet members.

The most recent Diet election was for the House of Representatives in December 2014, in which the LDP won a landslide victory.[44]  The next House of Representatives election will be held in 2018, unless the House is dissolved earlier.  The most recent House of Councillors election was in July 2013, and also resulted in a landslide victory for the LDP.[45]  The next House of Councillors election will be held in the summer of 2016.

The voter turnout rate has been falling in recent years, hitting a record low of 52.66% in the 2014 House of Representatives election.[46]  The highest percentage of voters are in their sixties, followed by voters in their fifties.[47]  

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V.  Legislative Process

Legislation can be submitted by Diet members,[48] a Diet committee,[49] or the Cabinet.[50]  When members of the House of Representatives submit a legislative bill, the bill must have the support of twenty or more members.  In the case of the House of Councillors, the bill must be supported by ten or more members.[51]  Legislative bills requiring the passage of a budget, however, must have the support of fifty of more members of the House of Representatives or twenty or more members of the House of Councillors.[52]

Bills are usually submitted to the House of Representatives first, but this is not always the case.[53]  For example, at the beginning of a Diet session, the House of Councillors can receive bills first; otherwise, the House would have no bills to discuss until the House of Representatives passed a bill and sent it to the House of Councillors.  Once a bill has been submitted to a house, the Chairman of that house refers the bill to the committee with jurisdiction over the bill.[54]  After receiving a briefing on the bill from the members who submitted the bill or from the minister of state in charge, the committee members question the members who submitted the bill, the minister of state, or other government officials regarding the bill.[55]  A vote is then taken in committee and the bill is sent to the plenary session, unless the committee decides that it is not necessary to do so.[56]  Once a bill is passed by the plenary session of a house, it is sent to the other house.[57]  When the other house also passes the bill, the bill becomes an act[58] and is sent to the Emperor through the Cabinet.[59]  All ministers of state and the Prime Minister must sign the act.[60]  The Emperor then promulgates the act within thirty days by publication in the official gazette.[61] 

Regarding the national budget,[62] the Cabinet makes a budget and submits it to the Diet for its decision.[63]  The House of Representatives makes a decision on it first.  If the House of Councillors’ decision on the budget differs from that of the House of Representatives and no agreement can be reached in a joint committee of both houses, or if the House of Councillors fails to take final action within thirty days after receiving the budget passed by the House of Representatives, the decision of the House of Representatives stands as the decision of the Diet.[64]

When the Cabinet submits a treaty for approval to the Diet,[65] the approval process is the same as for a budget—it is sent to the House of Representatives first, and the House of Representatives has control over the final decision .[66]

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Prepared by Sayuri Umeda
Foreign Law Specialist
January 2016


[1] The Promulgation of the Meiji Constitution and Educatron [sic], Ministry of Education, Culture, Sports, Science and Technology, http://www.mext.go.jp/b_menu/hakusho/html/others/detail/1317324.htm (last visited Dec. 4, 2015), archived at https://perma.cc/TT6K-WGHJ.

[2] 9. 大日本帝国憲法の発布 [Promulgation of Great Japan Imperial Constitution], National Archives of Japan, http://www.archives.go.jp/exhibition/digital/modean_state/contents/constitutional-law/index.html (last visited Dec. 4, 2015), archived at https://perma.cc/JVV5-JA4B.

[3] From Imperial Diet to National Diet, House of Representatives, http://www.shugiin.go.jp/internet/itdb_english. nsf/html/statics/guide/imperial.htm (last visited Dec. 4, 2015), archived at https://perma.cc/359V-2Y38.

[4] Constitution of Japan (1946), translation available on Prime Minister and His Cabinet’s website at http://japan.kantei.go.jp/constitution_and_government_of_japan/constitution_e.html, archived at https://perma.cc/D2PP-FT57.

[5] 衆議院議員選挙法中ヲ改正ス [Amending House of Representatives Election Act], National Archives of Japan, http://www.archives.go.jp/ayumi/kobetsu/s20_1945_06.html (last visited Dec. 4, 2015), archived at https://perma.cc/KJ2Z-AHYE; House of Councillors Member Election Act, Act No. 11 of 1947, abolished by Act on Implementation of House of Councillors Act and Reorganization of Related Acts, Act No. 101 of 1950, art. 1.

[6] National Archives of Japan, supra note 5.

[7] 詳細年表 5, 1946年12月1日~1947年6月23日 [Detailed Chronology 5 December 1, 1956–June 23, 1947], National Diet Library, http://www.ndl.go.jp/constitution/etc/history05.html (last visited Dec. 4, 2015), archived at https://perma.cc/QB4J-MT97.

[8]皇室令及附属法令廃止ノ件 [Regarding Abolishment of Imperial House Order and Related Laws and Regulations], Imperial House Order No. 12 of 1947, available at http://www.geocities.jp/nakanolib/kou/ks22-12.htm, archived at https://perma.cc/32XT-LXDM (click “Uploaded page”).

[9] The National Diet, House of Representatives, http://www.shugiin.go.jp/internet/itdb_english.nsf/html/ statics/guide/dietfun.htm (last visited Dec. 4, 2015), archived at https://perma.cc/8MM7-HWHE

[10] Constitution arts. 1 and 4.

[11] Id. art. 41.

[12] John Spacey, 4 Things to Do in Nagatacho, Japan Talk (Sept. 6, 2014), http://www.japan-talk.com/jt/ new/nagatacho-in-tokyo, archived at https://perma.cc/HMB2-73DL.

[13] Diet Building Facilities, House of Representatives, http://www.shugiin.go.jp/internet/itdb_english. nsf/html/statics/guide/bldg.htm (last visited Dec. 4, 2015), archived at https://perma.cc/KYS7-932S

[14] Constitution arts. 41–42.

[15] Id. art. 65.

[16] Id. art. 72.

[17] Parliamentary Cabinet System, House of Representatives, http://www.shugiin.go.jp/internet/itdb_ english.nsf/html/statics/guide/parliamentary.htm (last visited Dec. 8, 2015), archived at https://perma.cc/T86Z-RTTS.

[18] Constitution art. 67, para. 1.

[19] Id. art. 66, para. 3.

[20] Id. art. 69.

[21] Powers of the National Diet, House of Representatives, http://www.shugiin.go.jp/internet/itdb_english.nsf/ html/statics/guide/powers.htm (last visited Dec. 8, 2015), archived at https://perma.cc/X4NN-V3CC.

[22] Id.; Essay Comparing the Japanese and American Electoral Systems, in The Government of Modern Japan: Elections, Asia for Educators, Columbia University (2009), http://afe.easia.columbia.edu/special/japan_ 1900_elections.htm, archived at https://perma.cc/3253-JLDY.

[23] Constitution art. 1.

[24] 天皇と国民の憲法 「元首」と定め地位明確に [Emperor and People’s Constitution, Make the Position Clear by Stating “Head of State”], Sankei Newspaper (Apr. 27, 2013), http://www.sankei.com/politics/news/ 130427/plt1304270013-n2.html, archived at https://perma.cc/NQ8Y-5WPY.

[25] Public Offices Election Act, Act No. 100 of 1950, amended by Act No. 60 of 2015, art. 4; Asia for Educators, supra note 22; 衆議院小選挙区の区割りの改定等について [Regarding Amendment of Allocation of Small Election Districts], Ministry of Internal Affairs and Communication (June 28, 2013), http://www.soumu. go.jp/senkyo/senkyo_s/news/senkyo/shu_kuwari/index.html, archived at https://perma.cc/PV2Y-2ZD2; 衆議院比例代表選挙の選挙区(ブロック)と各選挙区別定数 [House of Representatives Proportional Representation Districts (Blocks) and Number of Seats in Each District] (map), Ministry of Internal Affairs and Communication (June 25, 2000), http://www.soumu.go.jp/senkyo/senkyo_s/news/senkyo/shu_teisu/pdf/map.pdf, archived at https://perma.cc/VG7E-APNM.

[26] Constitution art. 45.

[27] Id. art. 46.

[28] Public Offices Election Act art. 10.

[29] Diet Act, Act No. 79 of 1947, amended by Act No. 86 of 2014, art. 17.

[30] Id. art. 18.

[31] Id. art. 19.

[32] Types of Committees, House of Representatives, http://www.shugiin.go.jp/internet/itdb_english.nsf/html/ statics/guide/types.htm (last visited Dec. 8, 2015), archived at https://perma.cc/F426-PTME

[33] Standing Committees, House of Representatives, http://www.shugiin.go.jp/internet/itdb_english. nsf/html/statics/guide/committees.html (last visited Dec. 8, 2015), archived at https://perma.cc/6XVG-7LKJ.

[34] Types of Committees, supra note 32.

[35] Jonathan Soble, Portrait of Japan’s Main Political Parties, Financial Times (Dec. 16, 2012), http://www.ft. com/cms/s/0/9281ca7c-4742-11e2-a899-00144feab49a.html (by subscription).

[36] Poll, TV Station, http://www.tv-asahi.co.jp/hst/poll/graph_seitou.html (last visited Dec. 8, 2015), archived at https://perma.cc/43TT-MMQW

[37] UPDATE: Abe’s LDP Dominates Election; Noda Resigns After DPJ Humiliation, Asahi Shimbun (Dec. 17, 2012), http://ajw.asahi.com/article/behind_news/politics/AJ201212170006, archived at https://perma.cc/G6F5-SGEU.

[38] Political Parties, Japan Links, http://web-japan.org/links/government/political/political.html (last visited Dec. 8, 2015), archived at https://perma.cc/9A72-829M.

[39] For more information, see the website of the Japanese Communist Party, http://www.jcp.or.jp/english/.

[40] Soble, supra note 35.

[41] Constitution art. 45.

[42] Public Offices Election Act art. 31, para. 1.

[43] Constitution art. 46.

[44] 自公が圧勝325議席…民主伸び悩み、維新苦戦 [LDP-Komei Landslide Victory with 325 Seats . . . Democrats Failed to Gain More Seats, Innovation Had Hard Fight], Yomiuri Newspaper (Dec. 15, 2014), http://www.yomiuri.co.jp/election/shugiin/2014/news/20141215-OYT1T50011.html, archived at https://perma.cc/KW4E-DELF.

[45] 参院選 2013 [House of Councillors Election 2013], Yomiuri Newspaper, http://www.yomiuri.co. jp/election/sangiin/2013, archived at https://perma.cc/M2W5-XD9Z (click on “Screen capture” tab).

[46] 国政選挙における投票率の推移 [Changes of Voter Turnout Ratio in National Elections], Ministry of Internal Affairs and Communication, http://www.soumu.go.jp/senkyo/senkyo_s/news/sonota/ritu (last visited Dec. 8, 2015), archived at https://perma.cc/Y55R-B5Q9.

[47] 国政選挙における年代別投票率について [Regarding Voter Turnout Ratio in National Elections by Age Groups], Ministry of Internal Affairs and Communication, http://www.soumu.go.jp/senkyo/senkyo_ s/news/sonota/nendaibetu (last visited Dec. 8, 2015), archived at https://perma.cc/T6VL-QZGN.

[48] Diet Act art. 56.

[49] Id. art. 50-2.

[50] Cabinet Act, Act No. 79 of 1947, amended by Act No. 86 of 2014.

[51] Diet Act art. 56, para. 1.

[52] Id.

[53] 参議院のあらまし [Abstract of the House of Councillors], House of Councillors, http://www.sangiin.go.jp/ japanese/aramashi/houritu.html (last visited Dec. 8, 2015), archived at https://perma.cc/CKW9-2J9Y

[54] Diet Act art. 56, para. 2.

[55] Deliberation of Bills, House of Representatives, http://www.shugiin.go.jp/internet/itdb_english.nsf/ html/statics/guide/deliberation.htm (last visited Dec. 8, 2015), archived at https://perma.cc/K6D7-8C96.

[56] Diet Act art. 56, para. 2.

[57] Id. art. 83.

[58] Constitution art. 59, para. 1.

[59] Diet Act art. 65, para. 1.

[60] Constitution art. 74.

[61] Id. art. 7, item 1; Diet Act art. 66.  Promulgation by official gazette is a custom.  Minori Iba, 官報[Official Gazette], Rippo to Chosa, No. 318 (July 2011), available on Legislative Bureau, House of Councillors’ website, at http://houseikyoku.sangiin.go.jp/column/column090.htm, archived at https://perma.cc/DA5S-4G2Q.

[62] Constitution art. 86.

[63] Id. art. 73.

[64] Id. art. 60.

[65] Id. art. 73.

[66] Id. art. 61.

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Last Updated: 02/12/2016