A fuel cell system includes a reformer, a fuel cell, a desulfurizer, a recirculation passage through which the reformer communicates with the desulfurizer such that a part of the anode gas generated in the reformer flows into the desulfurizer, and an orifice member provided on the recirculation passage. The orifice member or at least a part of an inner wall of a portion that constitutes an upstream side from the orifice member in the recirculation passage is made of a material containing a material having an antifungal action.