A fuel cell system incorporated in a vehicle has a main electric motor, a drive power transmitting mechanism for engaging and disengaging a fuel gas pump, a coolant fluid pump, a supercharger, and a compressor, which serve as auxiliary equipment, and transmitting a drive power to the auxiliary equipment, and an auxiliary electric motor coaxially connectable to the main electric motor for transmitting a drive power to the auxiliary equipment depending on the manner in which the vehicle is operated.