FUEL CELL SYSTEM

This fuel cell system 1 provides a fuel cell system that can be reduced in cost. This fuel cell system 1 includes a reformer 11 for reforming raw fuel using a burner 15 to generate reformed gas, and a CO shift converter 12 shaped like a tube provided integrally with the reformer 11 such that the reformer 11 is positioned in the tube, for reducing a carbon monoxide concentration in the reformed gas generated by the reformer 11. In the fuel cell system 1, the CO shift converter 12 can be heated with exhaust gas from the burner 15 to increase the temperature thereof. Therefore, the need for a heater to increase the temperature of the CO shift converter 12 can be eliminated.