A fuel cell system includes: a fuel cell that generates an electric power and heat by a reaction of a reaction gas; a heat exchanger; a coolant circuit for a coolant between the fuel cell and the heat exchanger; a coolant circulating pump for circulating the coolant in the coolant circuit; and a drive motor for driving the coolant circulating pump, the coolant receiving and carrying the heat to the heat exchanger by the coolant circuit, the coolant circulating pump, and the drive motor. A rotational speed of the drive motor is controlled according to an upper limit of the rotational speed of the drive motor which may be determined on the basis of a cooling capacity of the heat exchanger, a speed of the vehicle mounting the fuel cell system, a generated electric power, and a flow rate of the reaction gas.