The present invention is a solid oxide fuel cell device (1), having a fuel cell module (2) furnished with a plurality of fuel cell units (16); fuel supply means (38) for supplying fuel; generating oxidant gas supply means (45) for supplying oxidant gas for generation; combustion section placed at one end portion of the solid oxide fuel cell units for combusting fuel; and control means for controlling the fuel supply means and generating oxidant gas supply means, and executing the startup mode operation for raising the solid oxide fuel cell units to a predetermined temperature, as well as the generating mode operation for outputting electrical power; whereby during the startup mode operation, the control means generates a weak power smaller than the generation startup power, raising the temperature of the solid oxide fuel cell units by the heat of generation.