FUEL CELL SYSTEM

To provide a fuel cell system configured to suppress irreversible performance degradation of a fuel cell. A fuel cell system wherein the controller preliminarily stores a data group indicating a relationship between, when a predetermined amount of hydrogen gas is supplied from the fuel gas supplier, an amount of the supplied hydrogen gas and a hydrogen pressure increase rate; wherein the controller calculates a fuel gas pressure increase rate from a pressure change detected by the pressure sensor when the fuel gas is supplied to the fuel cell; wherein the controller determines whether or not the fuel gas pressure increase rate is smaller than the hydrogen pressure increase rate; and wherein, when the controller determines that the fuel gas pressure increase rate is smaller than the hydrogen pressure increase rate, the controller prohibits power generation of the fuel cell.