PROBLEM TO BE SOLVED: To provide a cap sterilization device capable of surely sterilizing a cap even when accelerating the conveyance speed of the cap.SOLUTION: A cap sterilization device 50 is equipped with an introduction chamber 52, a sterilant spray chamber 53 and an air rinse chamber 54. The air in at least the introduction chamber 52 and air rinse chamber 54 is exhausted. Both exhaust pressures E2 and E4 of the introduction chamber 52 and the air rinse chamber are higher than the exhaust pressure E3 of the sterilant spray chamber 53, or the chamber 53 is not exhausted.SELECTED DRAWING: Figure 2