NOVELTY - The carbon monoxide (CO) removal device has a modifier that emits combustion exhaust gas from the burner through a combustion exhaust gas flow path (63). A reformed gas flow path (61) surrounding the combustion exhaust gas flow path, circulates the reformed gas with the oxidizing agent gas. An electric heater (66) heats the CO removal catalyst layer (62) provided in the combustion exhaust gas flow path, to a temperature with respect to temperature of combustion exhaust gas from the modifier, for removing the CO from the reformed gas.    USE - For fuel cell electric power generation system (claimed) such as solid polymeric electrolyte fuel cell (PEFC) electric power generation system.    ADVANTAGE - The CO removal catalyst layer is heated to optimum temperature within a short time and the whole CO removal catalyst layer is maintained to an optimal temperature uniformly for removing CO from the reformed gas.    DETAILED DESCRIPTION - A cooling air flow path (64) and cooling water flow path (65) are provided to cool the CO removal catalyst layer. The heat transfer promotion material layers (91,95) formed in the combustion flow path and coolant gas flow path, are filled with the granular heat transfer promotion material. A connection structure connects the downstream and upstream side of the reformed gas flow path to flow reformed gas between the flow path sides. INDEPENDENT CLAIMS are included for the following:    (1) fuel cell electric power generation system which has a fuel cell supplied with reformed gas to remove CO from the reformed gas; and    (2) temperature rising operating method of CO removal device, which involves rising the heating temperature of CO removal catalyst layer by the circulating the combustion exhaust gas. The circulation of combustion exhaust gas is stopped, when the temperature of the combustion exhaust gas or the temperature of CO removal catalyst layer reaches predetermined temperature. The CO removal catalyst layer is heated by circulating water vapor steam generated by heating the exhaust gas and by heat emission of selection oxidation reaction by circulating the reformed gas until the CO removal catalyst layer reaches to optimal temperature.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional diagram of the CO removal device. (Drawing includes non-English language text)    Reformed gas flow path (61)    CO removal catalyst layer (62)    Combustion exhaust gas flow path (63)    Cooling air flow path (64)    Cooling water flow path (65)    Electric heater (66)    Heat transfer promotion material layers (91,95)