PURPOSE: To provide a device supplying process gas to a semiconductor wafer producing and processing device.

CONSTITUTION: The raw material gas from a raw material gas tank 1 is evaporated by an evaporator 2 to form process gas which is, in turn, reduced in pressure to be supplied to a semiconductor wafer producing and processing devices 6 through a purifier 4 and a supply pipe 5. In this case, a check valve 9 is provided to the outlet part of a pressure reducing valve 3 and a recovery pipe 10 is arranged to the inlet parts of the producing and processing devices 6. The discharge valves 11 connecting the recovery pipe 10 and the supply pipe 5 are attached to the terminal parts of the devices 6 and a compressor 12, a receiver tank 13, a cooler 14 and a check valve 15 are successively connected between the recovery pipe 10 and the outlet part of the check valve 9 to constitute a process gas recirculating piping system.