On a start of a fuel cell system, (i) when the temperature of a high-voltage secondary battery obtained from a temperature sensor is higher than a predetermined reference value, a controller of the fuel cell system is configured to set an output voltage on a step-down side of a DC-DC converter to a higher voltage than a voltage of a low-voltage secondary battery and subsequently start an FC auxiliary machine using electric power from the high-voltage secondary battery. (ii) When the temperature of the high-voltage secondary battery obtained from the temperature sensor is equal to or lower than the predetermined reference value, on the other hand, the controller of the fuel cell system is configured to set the output voltage on the step-down side of the DC-DC converter to a lower voltage than the voltage of the low-voltage secondary battery and subsequently start the FC auxiliary machine using the electric power from the high-voltage secondary battery.