Solid oxide fuel cell device

The present invention is a solid oxide fuel cell device (1) with a load following function for changing a fuel supply rate in response to a load defined as a required power determined by demand power. The solid oxide fuel cell device of the present invention comprises a fuel cell module (2) having a fuel cell stack (14) composed of a plurality of solid oxide fuel cells and a reformer (20) for reforming fuel and supplying the fuel to the fuel cells; an inverter (54) for receiving electrical power generated by the fuel cell module (2) and converting the power to alternating power; a command power value setting device (111) for setting a command power value to be generated by the fuel cell module (2) based on the amount of load; a fuel control device (38) for determining a fuel supply rate supplied to the fuel cells and supplying the fuel so as to generate the above command power value; an inverter permitted power value instruction device for instructing to the inverter an inverter (54) permitted power value corresponding to the above command power value, which is the permitted amount of power to be extracted from the fuel cell module (2), after the fuel has been supplied to the fuel cells by the fuel control device (38); and an inverter permitted power value change device (110) for changing the amount of change per unit time in the next inverter permitted power value and outputting the amount of change unit time to the inverter permitted power value instruction device; wherein the inverter permitted power value change device (110) presets a plurality of proportionality characteristics indicating the differing multiple amounts of change per unit time, selecting one proportionality characteristic from among multiple proportionality characteristics based on the status of load, changing the amount of change per unit time in the next inverter permitted power value by using the selected proportionality characteristic.