A method of sterilizing a bottle includes steps of: sterilizing bacteria adhering to a preform made of resin by gasifying a sterilizer, discharging a sterilized gas from a nozzle toward a preform, now traveling, so as to adhere to the preform; activating the sterilizer adhering to the preform by blasting hot air to the preform; sterilizing the bacteria adhering to the preform, and removing the sterilizer adhering to the preform; heating the preform to a temperature suitable for blow-molding treatment; and blow-molding the preform within a mold to mold the preform into a bottle, wherein the above steps are performed sequentially in order. According to the above-mentioned steps, the sterilizer does not enter a blow-molding machine.