PROBLEM TO BE SOLVED: To prevent drying of adhered moisture from becoming insufficient due to freezing of the adhered moisture when desiring to dry the moisture adhered to a material to be sterilized or the like prior to sterilizing treatment.SOLUTION: There is provided a sterilization method for sterilizing a material to be sterilized by charging a sterilant in a sterilizing chamber which is heat insulation-controlled so that the internal temperature thereof is a prescribed level above the room temperature and is decompressed to a prescribed pressure. In the method, the material to be sterilized is left in the sterilizing chamber whose inside pressure is maintained to a first level prior to sterilization treatment for a prescribed time, and then the pressure of the sterilizing chamber is reduced from the first level to a second level which is below the first level and under which moisture does not freeze.SELECTED DRAWING: Figure 2【課題】被滅菌物等に付着した水分を、滅菌処理をする前に乾燥させたい場合に、付着している水分が凍ってしまい、付着している水分の乾燥が不十分になることを防止する。【解決手段】内部温度が室温以上の所定温度になるように滅菌室が保温管理されている滅菌室を所定圧まで減圧にした滅菌室に滅菌剤を投入することで被滅菌物を滅菌する滅菌処理を行う滅菌方法において、滅菌処理を行う前に、滅菌室内が第１の圧力に維持されている滅菌室の中に、被滅菌物を所定時間放置して、滅菌室の圧力を第１の圧力から、第１の圧力以下で水分が凍結しない第２の圧力まで減圧する。【選択図】 図２
