The Cabinet Legislation Bureau (内閣法制局, naikakuhōseikyoku) is a Japanese government agency which advises Cabinet members on drafting legislation to be proposed to the Diet.

It acts as legal counsel for the Cabinet by examining bills, orders, and treaties.

It interprets existing laws and pending legislation for the Executive Branch.

The Constitutional Archives Research Office is also located in the First Department.

It examines pending legislative bills, draft Cabinet orders, and draft treaties that relate to the Financial Services Agency; the Ministry of Internal Affairs and Communications; the Ministry of Foreign Affairs; the Ministry of Finance; and the Board of Audit.