To provide a carbon monoxide removing apparatus having a catalyst useful for selectively oxidizing carbon monoxide in a hydrogen-enriched reformed gas with oxygen with which carbon monoxide in the gas can be more efficiently oxidized and the amount of carbon monoxide can be reduced.

The reformed gas supplied into the carbon monoxide removing apparatus 11 is first passed through a catalyst layer 12 constituted of a catalyst A in which ruthenium and platinum are supported on a porous carrier in a weight ratio of ruthenium to platinum of ≥0.7 and ≤9.5 and ruthenium and platinum are localized in the outer surface of the porous carrier, then the reformed gas is passed through a catalyst layer 13 constituted of a catalyst B in which ruthenium and platinum are supported in a porous carrier in a weight ratio of ruthenium to platinum of ≥0.1 and <0.7 and ruthenium and platinum are localized in the outer surface of the porous carrier, and further the reformed gas is passed through a catalyst layer 14 constituted of the above catalyst A.