A solid oxide fuel cell (SOFC) device comprises a fuel cell assembly, a reformer, a fuel gas supply device, a water supply device, a reforming air supply device, a power generating air supply device, an ignition device, and a control device, the control device controls the fuel gas supply device, the water supply device, the reforming air supply device, the power generating air supply device, and the ignition device to conduct a combustion operation, then supply the fuel gas and the reforming air into the reformer to conduct a partial oxidation reforming reaction (POX) operation, then supply the fuel gas, the reforming air and water into the reformer to conduct an auto-thermal reforming reaction (ATR) operation, and then supply the fuel gas and water into the reformer to conduct a steam reforming reaction (SR) operation, thereby starting the solid oxide fuel cell device, and the control device controls the fuel gas supply device to hold constant the supply flow rate of fuel gas during a predetermined interval, controls the ignition device to ignite the fuel gas at the middle of the predetermined interval, and controls the fuel gas supply device to reduce the supply flow rate of fuel gas after an elapse of the predetermined interval.