NOVELTY - The carbon monoxide reduction apparatus (2) has reduction device (5) and heat exchanger (8). The device (5) comprises container (9) provided with upstream catalyst layer (10), downstream catalyst layer (11), internal heat exchanger (12) and mixing unit (6). A reformed gas containing hydrogen and carbon monoxide is cooled with exchanger (8) and flowed through catalyst layer (10). The reformed gas is then cooled with exchanger (12) and flowed through catalyst layer (11) at temperature less than temperature of layer (10), and carbon monoxide content is reduced.    USE - Carbon monoxide reduction apparatus is used for reducing carbon monoxide in reformed gas containing hydrogen and carbon monoxide (claimed).    ADVANTAGE - The carbon monoxide reduction apparatus is compact, inexpensive, and reduces carbon monoxide in hydrogen rich reformed gas efficiently by simple method.    DETAILED DESCRIPTION - The carbon monoxide reduction apparatus (2) has a carbon monoxide reduction device (5) and an inlet port heat exchanger (8). The reduction device (5) comprises a container (9) provided with an upstream catalyst layer (10), a downstream catalyst layer (11), an internal heat exchanger (12) and a mixing unit (6) to mix reformed gas and oxidized air, arranged in entrance side of container (9). A reformed gas containing hydrogen and carbon monoxide, flowing into the container is cooled with heat exchanger (8) and flowed through catalyst layer (10) maintained at predetermined temperature. The reformed gas is then cooled with heat exchanger (12) and flowed through catalyst layer (11) maintained at temperature less than temperature of catalyst layer (10), and carbon monoxide content is reduced. Temperature of heat exchanger (8) and heat exchanger (12) are controlled mutually.    DESCRIPTION OF DRAWING(S) - The drawing shows the process flowchart of the carbon monoxide reduction apparatus.    Carbon monoxide reduction apparatus (2)    Carbon monoxide reduction device (5)    Mixing unit (6)    Inlet port heat exchanger (8)    Container (9)    Upstream catalyst layer (10)    Downstream catalyst layer (11)    Internal heat exchanger (12)