A fuel cell system capable of adequately controlling the water content of a fuel cell is provided. An impedance reference value is stored in a memory 151 for an impedance comparator 150. The impedance reference value is a reference value that is set in order to prevent the water content in a fuel cell 40 from decreasing too much. The impedance comparator 150 compares a measured impedance value supplied from an impedance operation unit 140 with the impedance reference value and performs scavenging control based on the comparison result.
