In a fuel cell system in which load electric power is supplied from a fuel cell and a secondary battery, intermittent operation is performed, that is, operation of the fuel cell is stopped and the load electric power is supplied from the secondary battery in a low load region. At this time, a threshold value for stopping and starting the operation of the fuel cell is adjusted according to open circuit voltage. Thus, it is possible to prevent fuel from being unnecessarily consumed in order to maintain the open circuit voltage at a predetermined value when the operation of the fuel cell is stopped, and to improve response of the fuel cell when the operation of the fuel cell is restarted after the open circuit voltage has decreased in the fuel cell that has stopped generating electric power.