FUEL CELL SYSTEM

A fuel cell system includes: a fuel cell in which a plurality of cells is stacked; a cathode gas supply unit that supplies a cathode gas to the fuel cell; a voltage sensor that measures the voltage of the fuel cell; and a control unit that maintains the voltage of the fuel cell within a predetermined voltage range by controlling a supply amount of the cathode gas during low-load operation in which a load is lower than in normal operation. The control unit determines that there is a cross-leakage abnormality in the fuel cell when the supply amount of the cathode gas required to maintain the voltage of the fuel cell within the predetermined voltage range exceeds a predetermined criterial threshold value during the low-load operation.