An object of the present invention is to provide a sterilization gas purifying closed system device that is capable of performing a sterilization process with an inexpensive configuration. In order to achieve the object, there is provided a sterilization gas purifying closed system device that performs a sterilization process on a sealed use area using a sterilization gas, the device including: a gas pipe connected to the use area via a first opening that is open or closed by opening or closing a first valve； and a catalyst area connected to the use area via a second opening that is open or closed by opening or closing a second valve, in which the sterilization gas is a hydrogen peroxide gas, in which platinum and palladium are provided as a catalyst in the catalyst area, in which when the sterilization process is performed, if the second valve is closed and the first valve is open, the hydrogen peroxide gas is introduced into the use area from the gas pipe via the first opening, and after the introduction, if the first valve is closed and the use area is brought into a sealed state, the sterilization process is performed using the hydrogen peroxide gas, and in which after a predetermined period of time, if the first valve and the second valve are open and a non-toxic gas is introduced from the gas pipe via the first opening, the hydrogen peroxide gas in the use area is introduced, in a push manner, into the catalyst area, and the hydrogen peroxide gas is purified.
