To improve the effect of sterilization of a preform or a container made of resin with hydrogen peroxide.A sterilization process is performed on a preform or container made of resin that is made primarily of polyethylene terephthalate after a corona discharge treatment is performed on an inner surface of the preform or container made of resin, the corona discharge treatment including a voltage application step of applying a voltage produced in a corona discharge to an electrode that is capable of passing through an opening part of the preform or container made of resin, an insertion step of inserting the electrode to which the voltage is applied into the preform or container made of resin through the opening part, and a bottom part treatment step of treating an inner surface of a bottom part of the preform or container made of resin by bringing the electrode close to the bottom part until the corona discharge from the electrode changes discharge mode, and the sterilization process including a hydrogen peroxide supplying step of blasting a mist or gas of hydrogen peroxide solution or a mixture thereof to the preform or container made of resin.
