The present invention discloses a fuel cell system that blocks the oxidant gas flow passage. This fuel cell system includes a fuel cell stack, the oxidant gas supply passage, the oxidant gas exhaust passage, the first valve and second valve of normally open type, the first motor that operates open and close operations of the first valve, the second motor that operates open and close operations of the second valve, and the ECU that controls the first motor and the second motor. This ECU controls the first valve and the second valve to be in the open state during the power generation in the fuel cell stack, thereby to open the cathode flow passage, and controls the first valve and the second valve to be in the close state after the power generation in the fuel cell stack is stopped, thereby to block the cathode flow passage. The fuel cell system of the present invention further includes the first solenoid device and the second solenoid device that lock the respective valve bodies of the first valve and the second valve so as to maintain the close state of the first valve and the second valve.