The present invention allows low-concentration hydrogen sulfide gas, which is generated at the time of regular inspection or start-up of a production plant, to be efficiently recovered and effectively supplied to a processing plant that uses hydrogen sulfide gas. In the invention, the hydrogen sulfide gas production plant is provided with a first supply pipe (14) that supplies hydrogen sulfide gas obtained from a sulfur recovery facility (13) to a processing plant X, and a second supply pipe (16) that is branched at a predetermined point (15) in the first supply pipe (14) and supplies the hydrogen sulfide gas from the sulfur recovery facility (13) to the processing plant X. The first supply pipe (14) has a concentration meter (22) that is provided on the upstream side than the branch point (15) and measures the concentration of the hydrogen sulfide gas. The first supply pipe (14) and the second supply pipe (16) have ON/OFF valves (23), (26), respectively, that are provided on the downstream side of the branch point (15) and perform ON/OFF control of the supply to the processing plant X through the supply pipe.