Abstract: The blow molding device (1) is provided with a heating means (4) for heating a preform (P) to a temperature appropriate for molding, an antimicrobial agent-spraying means (50) for spraying an antimicrobial agent on the preform (P), a hot forming means for stretch blow molding the preform into a bottle (B), and an irradiation device (7) irradiating electromagnetic waves or ultrasonic waves on the bottle. After the heating means (4) has heated the preform (P), the anti-microbial agent-spraying means (50) sprays the anti-microbial agent and sterilizes the preform (P) with hot antimicrobial agent. During subsequent stretch blow molding of the preform (P), the hot forming means performs additional drying of antimicrobial agent retained on the preform (P) in the hot state and additional sterilization. The irradiation device (7) irradiates electromagnetic waves or ultrasonic waves to degrade the anti-microbial agent remaining on the molded bottle (B) and further promote antimicrobial agent drying and sterilization.