PROBLEM TO BE SOLVED: To easily and surely sterilize by introducing a sterilizing agent into a decompression system with a simple configuration and control. SOLUTION: The treatment tank 2 is provided with a decompression means 3 for sucking and discharging the gas in the treatment tank 2 to the outside, and a decompression means 4 for introducing outside air into the decompressed treatment tank 2. As the depressurizing means 3, the exhaust passage 6 from the inside of the processing tank 2 is provided with a primary valve 7, a heat exchanger 8, a secondary valve 9, and a vacuum pump 10 in this order. The disinfectant generation unit 5 (18) for supplying the disinfectant of solid fine particles, liquid fine particles, or gas to the air in the treatment tank 2 alone or in a mixed state is provided in the treatment tank 2. In the sterilization operation, the sterilizing agent generated from the sterilizing agent generating unit 5 (18) is supplied into the treatment tank 2 with the primary valve 7 closed, while the vacuum pump 10 is on the downstream side of the primary valve 7. Is depressurized. Then, the primary valve 7 is opened with the secondary valve 9 closed, and the disinfectant is introduced into the heat exchanger 8. [Selection diagram] Fig. 1【課題】簡易な構成および制御で、減圧系統に除菌剤を導入して、容易に確実に除菌を図る。【解決手段】処理槽２と、この処理槽２内の気体を外部へ吸引排出する減圧手段３と、減圧された処理槽２内へ外気を導入する復圧手段４とを備える。減圧手段３として、処理槽２内からの排気路６に、一次弁７、熱交換器８、二次弁９および真空ポンプ１０を順に備える。固体微粒子、液体微粒子または気体の除菌剤を、単独または混在した状態で、処理槽２内の空気中に供給する除菌剤発生部５（１８）が、処理槽２に設けられる。除菌運転では、一次弁７を閉じた状態で除菌剤発生部５（１８）から発生させた除菌剤を処理槽２内に供給する一方、真空ポンプ１０により一次弁７よりも下流側を減圧する。その後、二次弁９が閉じられた状態で一次弁７を開けて、熱交換器８に除菌剤を導入する。【選択図】図１
