PROBLEM TO BE SOLVED: To provide a structure which feeds the sterilizing agent remaining in a vaporization chamber for gasification of sterilizing agent into a sterilization chamber, capable of reducing the waste of sterilizing agent while stimulating sterilization action.SOLUTION: The structure includes a first atmosphere release valve which is opened or closed for control of the conduction between a vaporization chamber for evaporation of a sterilizing agent before injection to a sterilization chamber and the atmosphere. After the sterilizing agent gas evaporated in the vaporization chamber by vacuuming the vaporization chamber with a vacuum pump is injected in the sterilization chamber, the first atmosphere release valve is opened while the vaporization chamber and the sterilization chamber are conducted, so that the vaporization chamber is conducted to the atmosphere.
