A control method for a fuel cell system including a solid oxide fuel cell, an anode gas and a cathode gas being supplied to the fuel cell, the fuel cell performing electric generation corresponding to a load, the fuel cell system controlling gas supply to the fuel cell and the electric generation. The control method including: an electric generating operation step of controlling flow rates of the anode gas and the cathode gas that flow into the fuel cell depending on a magnitude of the load; and a self-sustained operation step of causing the fuel cell to perform self-sustained operation when the load is equal to or less than a predetermined value. The self-sustained operation step includes a gas supply step of supplying the anode gas with a predetermined flow rate and the cathode gas with a predetermined flow rate to the fuel cell.