A fuel cell system includes: a reformer (4) configured to generate a reformed gas by using a raw material gas; a fuel cell (6) configured to generate electric power by using the reformed gas from the reformer (4) and air; a desulfurizer (3) configured to perform hydrodesulfurization of the raw material gas; a recycled gas passage (7) through which a part of the reformed gas is supplied as a recycled gas to a raw material gas passage (5) provided upstream of the desulfurizer (3); and a heat exchanger (8) configured to cause the recycled gas flowing through the recycled gas passage (7) to perform heat exchange with one of the raw material gas and the air.
