Abstract: The present invention is a method and an apparatus for performing heating and sterilizing treatment on the inside of a PET bottle with a low heat resistance securely and without thermal deformation thereof, where a steam jetting nozzle is inserted into the bottle from a mouth portion thereof to jet steam from the nozzle, the steam is circulated inside the bottle to be exhausted from the mouth portion, the steam is caused to contact with a bottle inner face securely, and simultaneously cooling water is sprayed on an outer face of the bottle so that thermal deformation of the bottle wall face is prevented.