After that, the agency slimed down its organization by transferring its office routine work of the Imperial Household Agency to other government agencies or separating some work from the agency, and changed from the Imperial Household Ministry to Kunaifu (Imperial Household Agency) along with the enforcement of the Constitution of Japan on May 3, 1947, and became one of agencies under the prime minister.
その後、宮内省の事務を他の政府機関に移管もしくは分離独立して機構の縮小を図り、1947年（昭和22年）5月3日の日本国憲法施行とともに、宮内省から宮内府となり、内閣総理大臣の所轄する機関となった。