The fuel cell system includes a fuel cell stack, a battery, a relay, a first voltage sensor, a second voltage sensor, and a control device. The control device is configured to be capable of executing a fixation detection process of the relay. The fixing detection process includes: giving a closing command to the relay; starting power generation of the fuel cell stack after giving a closing command to the relay; giving an opening command to the relay when the voltage obtained from the first voltage sensor becomes equal to or higher than the voltage obtained from the second voltage sensor after starting power generation; and determining that the relay is fixed when the voltage obtained from the first voltage sensor is equal to the voltage obtained from the second voltage sensor after giving the opening command to the relay.
