NOVELTY - The system has a controller including an anode gas concentration acquiring section to estimate anode gas concentration at a location where the anode gas concentration is locally lower within a power generation region of a fuel cell based on a control state of anode gas at time where a shutdown command is issued. A shutdown operation determination section determines whether to permit or prohibit shutting down power generating operation of the fuel cell based on the anode gas concentration that is estimated by the anode gas concentration acquiring section.    USE - Fuel cell system i.e. anode non-circulation type fuel cell system (claimed), for use in a vehicle. Can also be used as a circulating pulsation control fuel cell system.    ADVANTAGE - The system makes accurate decision on whether to permit or prohibit shutting down the power generation operation of the fuel cell according to anode gas concentration at a position when the anode gas concentration is made locally lower in the power generation region of the fuel cell, so that degradation in cathode catalyst can be suppressed during the time when the power generation is shut down. The system prevents the cathode catalyst from exceeding system tolerance and deteriorating during the shutdown of the power generation operation, thus preventing degradation in output response after restarting the power generation operation.    DETAILED DESCRIPTION - The anode gas is hydrogen.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow chart illustrating a process for determining whether to permit/prohibit transition to a shutdown of a fuel cell stack carried out by a fuel cell system executed by a controller.    Step for determining lowest anode gas concentration (S10)    Step for determining whether request is made to shut down power generation of fuel cell stack (S20)    Step for determining whether lowest anode gas concentration is greater than or equal to prescribed concentration (S30)    Step for shutting down power generation of fuel cell stack (S40)    Step for permitting power generation of fuel cell stack (S50)