A solid oxide fuel cell system comprising: a reformer configured to generate a hydrogen-containing gas by using a raw material and water or humidified air; a solid oxide fuel cell including an anode and a cathode , and configured to generate electric power by using the hydrogen-containing gas supplied from the reformer to the anode and air supplied to the cathode ; a heat radiator configured to radiate heat from at least one of an anode off-gas discharged from the anode and a combustion exhaust gas generated by combusting the anode off-gas to generate condensed water; a condensed water circulating passage configured to circulate the condensed water supplied from the heat radiator ; a condensed water tank provided on the condensed water circulating passage and configured to store the condensed water therein; a condensed water pump provided on the condensed water circulating passage and configured to circulate the condensed water; a condensed water/off-gas heat exchanger provided on the condensed water circulating passage and configured to exchange heat between the condensed water and an off-gas discharged from the solid oxide fuel cell to heat the condensed water by the off-gas; and a reforming water pump configured to supply to the reformer the condensed water as at least a part of the water supplied to the reformer ; or a humidifier provided on the condensed water circulating passage and configured to humidify air using the condensed water to generate the humidified air supplied to the reformer , characterized in that the condensed water pump circulates the condensed water in such a manner that the condensed water discharged from the condensed water pump flows through the condensed water/off-gas heat exchanger , and wherein the condensed water/off-gas heat exchanger is a plate heat exchanger or a double-pipe heat exchanger. a reformer configured to generate a hydrogen-containing gas by using a raw material and water or humidified air; a solid oxide fuel cell including an anode and a cathode , and configured to generate electric power by using the hydrogen-containing gas supplied from the reformer to the anode and air supplied to the cathode ; a heat radiator configured to radiate heat from at least one of an anode off-gas discharged from the anode and a combustion exhaust gas generated by combusting the anode off-gas to generate condensed water; a condensed water circulating passage configured to circulate the condensed water supplied from the heat radiator ; a condensed water tank provided on the condensed water circulating passage and configured to store the condensed water therein; a condensed water pump provided on the condensed water circulating passage and configured to circulate the condensed water; a condensed water/off-gas heat exchanger provided on the condensed water circulating passage and configured to exchange heat between the condensed water and an off-gas discharged from the solid oxide fuel cell to heat the condensed water by the off-gas; and a reforming water pump configured to supply to the reformer the condensed water as at least a part of the water supplied to the reformer ; or a humidifier provided on the condensed water circulating passage and configured to humidify air using the condensed water to generate the humidified air supplied to the reformer , characterized in that the condensed water pump circulates the condensed water in such a manner that the condensed water discharged from the condensed water pump flows through the condensed water/off-gas heat exchanger , and wherein the condensed water/off-gas heat exchanger is a plate heat exchanger or a double-pipe heat exchanger. <EOS>