To provide a solid oxide type fuel cell system that can continuously perform a water self-sustained operation while restraining a lack of modified water.

A solid oxide type fuel cell system comprises: a reformer 4 for vapor-modifying raw fuel; a solid oxide type fuel cell 6 for generating power by oxidizing and reducing modified fuel gas and an oxidation material; a blowing device 8 for supplying the oxidation material to the solid oxide type fuel cell 6; a fuel pump 34 for controlling a supply amount of the raw fuel; control means for controlling operations of the fuel pump 34 and the blowing device 8; condensation/recovery means 50 for condensing and recovering water vapor contained in combustion exhaust gas; and water supply means 52 for supplying the condensed and recovered water to the reformer 4. When an amount of the condensed and recovered water is smaller than a modification required amount, water self-sustained determination means determines that a water self-sustained operation is not satisfied, and the control means increases a power generation output of the solid oxide type fuel cell 6.