A sterilization process is performed on a preform or container made of resin after a corona discharge treatment is performed on an inner surface of the preform or container, the corona discharge treatment including applying a voltage produced in a corona discharge to an electrode that passes through an opening part of the preform or container, an insertion step of inserting the electrode to which the voltage is applied into the preform or container through the opening part, and a bottom part treatment step of treating an inner surface of a bottom part of the preform or container 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.