A blow molding device comprising: antimicrobial agent-spraying means for spraying a preform with an antimicrobial agent generating active oxygen or hydroxyl radical; heating means for heating the preform to a temperature appropriate for molding; hot forming means for stretch blow molding the preform into a bottle; and an irradiation device for irradiating the molded bottle with electromagnetic waves or ultrasonic waves, wherein the blow molding device is configured such that, after the heating of the preform by the heating means, the antimicrobial agent-spraying means is configured to spray the antimicrobial agent and sterilize the preform with the antimicrobial agent, wherein the blow molding device is configured such that during the stretch blow molding of the preform following the antimicrobial agent-spraying means, the hot forming means is additionally configured to dry the antimicrobial agent retained on the preform in the hot state and is additionally configured to sterilize the preform, wherein the blow molding device is configured such that, at a same time as the hot forming means, the irradiation device is configured to emit the electromagnetic waves or the ultrasonic waves to degrade the antimicrobial agent remaining on the molded bottle and further promote the drying of the antimicrobial agent and the sterilization of the preform, and wherein the antimicrobial agent-spraying means includes: a cover that is arranged above a mouth portion opened at an upper side of the preform and covers the mouth portion from above with a space between the cover and the mouth portion; and a pipe being inserted in the space of the cover for supplying and spraying the antimicrobial agent in a direction toward a bottom portion inside the preform; characterized in that the irradiation device is disposed amid the hot forming means. antimicrobial agent-spraying means for spraying a preform with an antimicrobial agent generating active oxygen or hydroxyl radical; heating means for heating the preform to a temperature appropriate for molding; hot forming means for stretch blow molding the preform into a bottle; and an irradiation device for irradiating the molded bottle with electromagnetic waves or ultrasonic waves, wherein the blow molding device is configured such that, after the heating of the preform by the heating means, the antimicrobial agent-spraying means is configured to spray the antimicrobial agent and sterilize the preform with the antimicrobial agent, wherein the blow molding device is configured such that during the stretch blow molding of the preform following the antimicrobial agent-spraying means, the hot forming means is additionally configured to dry the antimicrobial agent retained on the preform in the hot state and is additionally configured to sterilize the preform, wherein the blow molding device is configured such that, at a same time as the hot forming means, the irradiation device is configured to emit the electromagnetic waves or the ultrasonic waves to degrade the antimicrobial agent remaining on the molded bottle and further promote the drying of the antimicrobial agent and the sterilization of the preform, and wherein the antimicrobial agent-spraying means includes: a cover that is arranged above a mouth portion opened at an upper side of the preform and covers the mouth portion from above with a space between the cover and the mouth portion; and a pipe being inserted in the space of the cover for supplying and spraying the antimicrobial agent in a direction toward a bottom portion inside the preform; characterized in that the irradiation device is disposed amid the hot forming means. a cover that is arranged above a mouth portion opened at an upper side of the preform and covers the mouth portion from above with a space between the cover and the mouth portion; and a pipe being inserted in the space of the cover for supplying and spraying the antimicrobial agent in a direction toward a bottom portion inside the preform; characterized in that the irradiation device is disposed amid the hot forming means.