A blow molding machine is simply sterilized.The blow molding machine is sterilized by filling a preform (1) with a liquid sterilizer (P) containing an ethanol constituent or both an ethanol constituent and a hydrogen peroxide constituent, and blasting blow air into the preform (1) in a state where the liquid sterilizer (P) remains in the preform (1) to diffuse the liquid sterilizer (P).
