A fuel cell system of the present invention is mounted on a moving object and is equipped with a fuel cell for generating power by chemically reacting a fuel gas supplied to an anode and an oxidizer gas supplied to a cathode; a cooling mechanism for cooling the fuel cell by radiating heat of a refrigerant circulating in the fuel cell into an atmosphere; a speed detection mechanism for detecting a moving speed of the moving object; an outside air temperature detection mechanism for detecting an outside air temperature; a cooling amount estimation mechanism for estimating a cooling amount of the fuel cell by the cooling mechanism, based on the moving speed and the outside air temperature; and an upper limit value set mechanism for setting an upper limit value of a power generation current, based on an estimation result of the cooling amount estimation mechanism.