For implementing a stop control which extracts a current from a fuel cell and consumes a cathode side oxygen at a system stop, the current extraction from the fuel cell is ended in a state that a certain quantity of oxygen smaller than when the current extraction is started remains on a cathode side of the fuel cell. With this, the hydrogen movement to the cathode side after the system stop can be effectively suppressed and thereby a cathode internal hydrogen concentration at the system start can be kept low, thus making it possible to properly process the cathode side hydrogen at the system start.