The fuel cell system includes a humidifying unit for humidifying supply air to be supplied to the fuel cell, utilizing cooling water used for cooling the fuel cell. It also includes a pre-humidifying unit for humidifying the supply air beforehand with air discharged from the fuel cell, the pre-humidifying unit being positioned in the upstream of the humidifying unit within a supply air path. The cooling water, which recovered heat generated when the fuel cell generated electricity, releases heat in a cooling water heat radiator. The heat is then utilized for heating water which circulates in a hot water path and the hot water is stored in a hot water reserve tank.
