A fuel cell device according to the present invention includes a controller. The controller is configured to allow a fuel gas supply device and an oxygen-containing gas supply device to supply the fuel gas and the oxygen-containing gas supplied to fuel cells (19) in a supply amount less than a supply amount to be set in accordance with a decreased power as required by the external load as well as to cause an igniter to start operation if the power required by the external load decreases and flameout of the combustion in a combustor (45) is recognized.