A fuel cell comprising: a fuel cell stack in which a plurality of planar power generation cells are stacked in a thickness direction of the power generation cell , each of the plurality of planar power generation cells including an electrolyte layer , and a cathode and an anode disposed so as to sandwich the electrolyte layer therebetween, and generating electric power using oxidant gas and fuel gas; and a heat exchanger provided between two adjacent power generation cells in the stacking direction and in contact with said two adjacent power generation cells , the plurality of power generation cells being provided on both sides in the stacking direction of the heat exchanger, the heat exchanger including therein a first flow path for oxidant gas that passes the oxidant gas supplied from outside; and a second flow path for oxidant gas connected to an outlet side of the first flow path for oxidant gas of the heat exchanger and to the cathode side of each of the power generation cells , the second flow path for oxidant gas supplying the oxidant gas that has passed through the first flow path for oxidant gas to the cathode side of each of the power generation cells of the fuel cell stack on both sides in the stacking direction of the heat exchanger ; characterized in that the heat exchanger further includes a first flow path for fuel gas that passes fuel gas supplied from outside; and the fuel cell further comprises a second flow path for fuel gas connected to an outlet side of the first flow path for fuel gas of the heat exchanger and to the anode side of each of the power generation cells , the second flow path for fuel gas supplying fuel gas that has passed through the first flow path for fuel gas to the anode side of each of the power generation cells of the fuel cell stack on both sides in the stacking direction of the heat exchanger . a fuel cell stack in which a plurality of planar power generation cells are stacked in a thickness direction of the power generation cell , each of the plurality of planar power generation cells including an electrolyte layer , and a cathode and an anode disposed so as to sandwich the electrolyte layer therebetween, and generating electric power using oxidant gas and fuel gas; and a heat exchanger provided between two adjacent power generation cells in the stacking direction and in contact with said two adjacent power generation cells , the plurality of power generation cells being provided on both sides in the stacking direction of the heat exchanger, the heat exchanger including therein a first flow path for oxidant gas that passes the oxidant gas supplied from outside; and a second flow path for oxidant gas connected to an outlet side of the first flow path for oxidant gas of the heat exchanger and to the cathode side of each of the power generation cells , the second flow path for oxidant gas supplying the oxidant gas that has passed through the first flow path for oxidant gas to the cathode side of each of the power generation cells of the fuel cell stack on both sides in the stacking direction of the heat exchanger ; characterized in that the heat exchanger further includes a first flow path for fuel gas that passes fuel gas supplied from outside; and the fuel cell further comprises a second flow path for fuel gas connected to an outlet side of the first flow path for fuel gas of the heat exchanger and to the anode side of each of the power generation cells , the second flow path for fuel gas supplying fuel gas that has passed through the first flow path for fuel gas to the anode side of each of the power generation cells of the fuel cell stack on both sides in the stacking direction of the heat exchanger . <EOS>