Even in a case where a spark is generated in an electron beam irradiation device 28, all the vessels 2 now being conveyed are surely sterilized by the irradiation with the electron beam. The electron beam is emitted by heating filaments 42 arranged in a vacuum chamber 40, and the vessels 2 are irradiated with the electron beam taken out into atmosphere through a window foil 48 of an irradiation window 46 formed to an irradiation section 44. The vessels 2 are conveyed in a state of being held by vessel holding portions 36A and 36B of a vessel conveying device 24 and pass in front of the irradiation window 46. Although the electron beam irradiation is temporarily interrupted when a spark is generated, a length of the irradiation window 46 in a vessel conveying direction X is made larger than a vessel conveying distance in an interruption time.
