The present invention includes a fuel cell (11), a fuel gas supplying device (16), an oxidizing gas supplying device (17) and a control apparatus (20) and further includes at least one of a temperature control device (19) which controls the temperature of the fuel cell (11) and a humidifying device (24) which humidifies at least one of the fuel gas and the oxidizing gas to be supplied to the fuel cell (11), wherein: the control apparatus (20) controls at least one of the temperature control device (19), the humidifying device (24), the fuel cell (11) and the fuel gas supplying device (16) to cause the temperature of the fuel cell (11) to be equal to at least one of the dew point of the fuel gas and the dew point of the oxidizing gas, before cutting off an electrical connection between the fuel cell (11) and a load; and then the control apparatus (20) cuts off the electrical connection between the fuel cell (11) and the load.