The structure of the national government of Japan is important for understanding how laws are created and how administrative functions are executed.
The following vocabulary are key terms associated with the concepts discussed in this article:
The Constitution of Japan (1946) is the supreme law of the nation (Art. 98): no law, ordinance, imperial rescript or other act of government that is contrary to the constitution can have legal force or validity. This has two implications:
In addition to concepts such as citizen’s rights and duties; renunciation of war; the role of the emperor; etc., the Constitution is an important document that outlines the overarching structure of the Japanese government.
The Constitution was enacted by the National Diet on 29 October 1946; thus, it is called the Constitution of 1946. It was promulgated (i.e.) on 3 November of 1946, which is the date it was officially published in the National Gazette – an important step in enacting laws. However, it became effective, i.e. having legal force, on 3 May 1947.
The Constitution defines the Japanese national government has having three branches: legislative, executive, and judicial. It is different from the system in the US, in that it is a unitary parliamentary system, whereas the US is a federal republic.
The legislative organ of the state is the National Diet (国会). The Diet is analogous to the US Congress in the US as the legislative body of the state. The Diet is “bicameral” system (Art. 42), having a lower and upper house, called the House of Representatives (衆議院) and the House of Councilors (参議院), respectively. These are analogous to the House of Representatives and the Senate of the US Congress.
Members of each house are directly elected by the people (Art. 43).
The National Diet replaced the Imperial Diet (帝国議会) at the end of WWII with the enactment of 1946 Constitution. The Imperial Diet also had two houses: only members of the House of Representatives were directly elected by the people, and the House of Peers (貴族院), which was populated by nobles selected by the emperor.
Art. 41 of the Constitution specifies that the National Diet is the highest organ of state power and the sole law-making organ of the state. A bill becomes law when it is passed in both houses of the Diet.
Where the analogy between the National Diet of Japan and US Congress breaks down is in that the Diet is a parliamentary body. That is, the executive branch is dependent on the legislative branch. Whereas the US Constitution provides for greater separation between the legislative branch (Congress) and the executive (the President).
Further Reading
The Constitution, Art. 65, vests the Cabinet (内閣) with the executive power of the state. The Cabinet consists of a Prime Minister (総理大臣), as the head, and the other Ministers of State (国務大臣), and together they are responsible to the Diet for the exercise of executive powers (Art. 66).
The Cabinet Act (Act No. 5 of 1947) largely covers the same legal ground as the Constitution, Arts. 65 – 73, and it is the next law after the Constitution that establishes the framework of the Cabinet.
The Diet selects one of its members, from either house, to be the Prime Minister (Art. 67). The Prime Minister then appoints the Ministers of State, only a majority of which must be selected from the members of the Diet (Art. 68). The Prime Minister can remove ministers at will.
At this point, several differences between the parliamentary system and that of the US should be clear:
| Japanese System | US System |
|---|---|
| The chief executive originates out of the legislative body. | The executive and legislative branches are separate. |
| The people do not directly elect the executive. | While not elected by popular vote, citizens elect the President through the electoral college system. |
| The cabinet is responsible to the legislative body for the use of executive power. | The President does not receive authority to exercise executive power from Congress. |
The duties of the Prime Minister are outlined in Art. 72 and include control and supervision of the administrative branches of the government. The duties and other administrative functions of the Cabinet are outlined in Art. 73.
Next to the Constitution, the National Government Organization Act (Act No. 20 of 1948) is the next most important law in defining the structure of the “administrative organs of the State” under the control and jurisdiction of the Cabinet (Art. 1), excluding the Cabinet Office.
The administrative organs of State are set under the control of the Cabinet (Art. 2) and their organization is prescribed by this Act (Art. 3), however the scope and jurisdiction of each administrative organ is determined in separate laws (Art. 4).
The administration is chiefly divided into Ministries (省). Each ministry is headed by a minister of State, selected by the Prime Minister (Art. 5). Ministries have several types of internal and external associated organizations that work together under the supervision and control of the minister.
As of 2026, at the top level there are 11 ministries, along with two cabinet level agencies, a cabinet level commission and the Cabinet Office itself. Each of these key ministries has its own unique organizational structure to meet the administrative needs and goals entrusted to it. However, the structure and leadership of each of those ministries and associated organizations are governed by National Government Organization Act.
Organization charts of the Japanese national government can be found on the Cabinet Secretariat website, with English versions here: https://www.cas.go.jp/jp/gaiyou/jimu/jinjikyoku/satei_01_01.html
Further Reading