To apply a function of feeding a constant quantity of alcohol into a chamber each time to an alcohol vapor sterilizer.

In the alcohol vapor sterilizer, the chamber 3 in which a sterilized article is stored is sealed, a prescribed quantity of alcohol is injected into the chamber 3 and heated and pressurized, and the sterilized article stored in the chamber 3 is sterilized with the alcohol vapor. A diaphragm pump 5 is used as the injection device for injecting the prescribed quantity of alcohol into the chamber 3. The diaphragm type pump 5 can always secure a constant spouting quantity by reciprocating a diaphragm, and therefore, the prescribed quantity of alcohol can be injected into the chamber 3 by specifying the operation time of the diaphragm.