A step of letting a preform (1) made of resin adsorb a sterilizer, a step of sterilizing the preform (1) by heating the preform (1) having adsorbed the sterilizer to a temperature suitable for a blow-molding treatment to activate the sterilizer adsorbed by the preform (1) and a step of shaping the preform (1) into a bottle (2) by blowing aseptic air into the preform (1) in a mold (4) are performed sequentially. According to the above-mentioned steps, the sterilizer does not enter a blow-molding machine.
