When a request to stop an operation of a fuel cell system is issued, a control unit stops the operation of the fuel cell system and cuts off the electrical connection between the fuel cell and a drive motor by shutting OFF a power supply relay. Where a shift position signal indicating that the shift position SP is at the P or N position is received from a shift selector and the parking brake is set, the control unit determines whether a coolant temperature Tfc detected via coolant detection sensors is at or below 20.degree. C. If it is determined that the detected coolant temperature Tfc is at or below 20.degree. C., the control unit commences a temperature-maintenance operation process.