<;P>;PROBLEM TO BE SOLVED: To provide a sterilizer capable of surely sterilizing a cap by uniformly irradiating it with an electron beam. <;P>;SOLUTION: When scanning the electron beam and irradiating the cap 200 with the electron beam, an accelerated voltage E for generating an electron beam and scanning locus of the electron beam are changed during one scan. It is preferable to set up rotation speed of the cap 200 so as to make an angle of the cap 200 different per every scan of the electron beam. Thus, a uniformity in irradiation of the cap 200 with the electron beam is improved. <;P>;COPYRIGHT: (C)2008,JPO&INPIT