Provided is a fuel cell system. The fuel cell system comprises: a reformer that reforms fuel; a reformed fuel storage unit that receives the reformed fuel from the reformer and stores same; a fuel cell stack that generates electric power and heat by using the reformed fuel; a boiler unit that provides heating by using heating water, a battery unit that stores the electric power generated in the fuel cell stack; and a control unit that controls the operations of the reformer, the reformed fuel storage unit, the fuel cell stack, the boiler unit, and the battery unit, wherein the control unit controls the reformer to operate using the heating water of the boiler unit when the temperature of the heating water of the boiler unit is higher than a first baseline and the stored amount of the reformed fuel stored in the reformed fuel storage unit is equal to or less than a second baseline.

A fuel cell module (includes a first area where an exhaust gas combustor and a start-up combustor are provided, an annular second area around the first area and where a reformer and a heat exchanger are provided, and an annular third area around the second area and where an evaporator is provided. Second circumscribed non-uniform-flow suppression plates are provided along the minimum circumscribed circles which contact outer surfaces of heat exchange pipes of the heat exchanger.