PROBLEM TO BE SOLVED: To prevent inside of a chamber 2 from being polluted by a cap 4 when the cap 4 is imperfectly sterilized due to abnormal radiation of electron beam.SOLUTION: A cap 4 conveyed in an aseptic chamber 2 by a cap chute 6 is sterilized by radiating electron beam from an electron beam radiation device 8. The cap chute 6 has a free conveying section 6c in which the cap 4 is conveyed in a rolling manner, a regulated conveying section 6b for conveying the cap 4 while being regulated by a star wheel 10 on its upstream side, and a stopper means 18 on the upstream side of the regulated conveying section 6b. A reject means 20 is provided at a downstream part of the cap chute 6, at a position where the sterilization is completed by the radiation of the electron beam. When the electron beam is abnormally radiated, the cap 4 is stopped by the stopper means 18, and the cap 4 is rejected by the reject means 20.
