Solid oxide fuel cell system including heat exchanger disposed of exhaust-gas and loop circulation paths

A solid oxide fuel cell system includes a solid oxide fuel cell that produces electricity by using a hydrogen-containing gas and an oxidant gas, an exhaust-gas path via which an exhaust gas discharged from the solid oxide fuel cell flows, a circulation path via which a coolant circulates, a first heat exchanger that is disposed on the exhaust-gas path and the circulation path and enables heat exchange between the exhaust gas and the coolant, a second path, via which condensed water produced when the exhaust gas is cooled in the first heat exchanger flows, that branches from the exhaust-gas path and is connected to the circulation path, a second tank that stores reservoir water, and a second heat exchanger that is disposed in the second tank and on the circulation path and enables heat exchange between the reservoir water and the coolant.