PROBLEM TO BE SOLVED: To simultaneously perform dry type decontamination with respect to a dry type decontamination target chamber and also wet type decontamination with respect to a wet type decontamination target chamber.SOLUTION: In a preparation operation, the room inside of the dry type decontamination target chamber 1 is adjusted to be a temperature and humidity state for the dry type decontamination, where hydrogen peroxide vapor is hardly condensed, and also the room inside of the wet type decontamination target chamber 2 is adjusted to be a temperature and humidity state for the wet type decontamination, where hydrogen peroxide vapor is easily condensed. In a decontamination operation following the completion of the preparation operation, the amounts of supply of decontamination gas G with respect to the respective decontamination target chambers 1, 2 are individually adjusted, so that a dry type decontamination state Jdry appears in the dry type decontamination target chamber 1 and also a wet type decontamination state Jwet appears in the wet type decontamination target chamber 2.
