A fuel cell system includes a fuel cell including a fuel electrode being supplied with fuel gas and an oxidant electrode being supplied with oxidant gas and generating electric power by causing the fuel gas and the oxidant gas to react with each other, a voltmeter measuring an output voltage of the fuel cell, an ammeter measuring an output current of the fuel cell, a restricting valve provided upstream and downstream of an oxidant electrode side of the fuel cell and being opened in a power generation state and being closed in a stopped state or under the oxygen consuming control, and a load control unit controlling a current value of an output current to be output by the fuel cell and, under the oxygen consuming control, controlling the output voltage of the fuel cell such that the output current reduces as the output voltage of the fuel cell increases.