To provide a fuel cell system capable of suppressing deterioration of a catalyst. A fuel cell system, wherein the fuel cell system comprises a fuel cell, a fuel gas system, an oxidant gas system, a pressure sensor and a control unit; wherein the control unit is configured to supply a predetermined amount of a fuel gas to the fuel cell when the fuel cell system is stopped; and wherein the pressure sensor is configured to measure a pressure of the fuel gas present in the fuel gas system.