To supply different kinds of gas by a gas supply system.

The gas supply system 10 includes, in the same housing 12, a first gas supply path 20 for supplying CNG (compressed natural gas) and a second gas supply path 30 for supplying hydrogen (fuel cell gas). The first and second gas supply paths 20 and 30 are provided with a shared path 40. Control instruments such as a flow meter 100, a control valve 110, an isolation valve 120, a pressure sensor 130 and an exhaust valve 140 are arranged in the shared path 40. The exhaust valve 140 is installed in an exhaust path 42 branched from the shared path 40 is opened when a gas of a different kind from a previous one is to be supplied, or when hydrogen is to be supplied, thereby discharging the valve to residual gas in the shared path 40.