FUEL CELL SYSTEM

A fuel cell system includes a controller that controls an amount of air flow to be supplied from an air blower included in an oxygen-containing gas supply to a cell stack to cause a power level (in amperes) of a fuel cell controllable by a power level regulator (power conditioner) and an air utilization to have an increase-control section in which the air utilization increases in accordance with an increase in the power level of the fuel cell and a decrease-control section in which the air utilization decreases in accordance with an increase in the power level. The air utilization is a ratio of an air amount used by the fuel cell for power generation to an oxygen-containing gas (air) amount supplied to the fuel cell.