The Ministry of Justice (called the Shihosho) in the prewar days had jurisdiction over a broad range of legal and judicial matters. With the enforcement of the New Constitution in 1947, the matters pertaining to courts were transferred to the jurisdiction of the Supreme Court as the courts became independent from the Ministry of Justice.

In 1948, the following year, the Ministry of Justice was abolished and the Attorney General's Office (called the Homucho) with jurisdiction over all legal matters was established. The new Office, in addition to the work of the Ministry of Justice (Shihosho), was then entrusted with the work of the examination of drafting laws and regulations, and international treaties, which had been under the jurisdiction of the Legislative Bureau of the Cabinet; research and study of judicial and legal systems of other countries as well as matters pertaining to civil and administrative suits; and the work of the protection of human rights.

As a result of the reform of the administrative organization in 1949, the Attorney General's Office became the Ministry of Justice (called the Homufu) and was further reorganized as the Ministry of Justice (called the Homusho) in 1951, at which time the Attorney General and Assistants system was abolished and the Minister of Justice was placed as the head of the Ministry. At the same time, the work of the examination of drafting laws and regulations was returned to the jurisdiction of the Cabinet and the work of immigration control that had been a part of the work of the Ministry of Foreign Affairs was placed under the jurisdiction of the Ministry of Justice.