A control apparatus for a vehicle-mounted fuel cell power generation system in accordance with the invention predicts a possibility of collision of a vehicle. If determining that the possibility of collision is high (YES at S12), the control apparatus stops the fuel cell power generation system. By stopping the power generation before a collision occurs, the safety of the fuel cell power generation system can be improved. If after the system stops, a collision does not occur (NO at S16), the system is restarted. If a collision occurs (YES at S16), high-voltage relays are switched off to stop the supply of electric power from an electricity storage to various loads of the vehicle.