PURPOSE: To enable continuous power generation without cutting of fuel supply even if concentration of carbon monoxide becomes an allowable value or more, and dispense with a separate fuel supply system for backup by arranging a bypass line of a fuel supply line and a carbon monoxide removing device interposed in the bypass line.

CONSTITUTION: When CO concentration in fuel flowing in a fuel supply line 24 becomes an allowable value or more by a carbon monoxide detector 26, cutoff valves 30 and 31 are opened instantly through a control device unit 32 by a detecting signal of the detector 26, and a cutoff valve 27 is closed, and fuel of the fuel supply line 24 is switched to a bypass line 28. The fuel bypassed/ supplied to the bypass line 28 is introduced to an anode pole 21 through a carbon monoxide removing device 29. Carbon monoxide being a poisoning material of platinum used in a catalyst electrode of the anode pole 21 can protect a fuel cell (particularly, anode pole) since it becomes allowable concentration or less by the removing device 29. Since supply of the fuel to the anode pole 21 is not cut off, continuous operation of a fuel cell becomes possible.