Abstract: In 1999, Japan made a change in the epidemic prevention legislation system by abolishing the Infectious Diseases Law of “great executive power” and implementing the Infectious Diseases Law of “small executive power”. Although this change avoids the malpractice of “excessive epidemic prevention” in some infectious diseases that can be effectively controlled by the Infectious Diseases Law, it also causes the problem of insufficient emergency authority of Japanese epidemic prevention administration in response to special major epidemics. After that, Japan supplemented this deficiency by enacting the New Influenza Special Measures Act. In 2020, Japan passed special legislation to expand the scope of application of the New Influenza Special Measures Act, which not only gives administrative agencies certain special measures in response to the coronavirus pandemic, but also sets a legislative precedent for responding to other major emerging infectious disease outbreaks in the future.

Key words: administrative authority, epidemic prevention legislation, declaration of emergency