NOVELTY - A carbon monoxide (CO) removal system has fuel supply path (12) which supplies fuel gas to the fuel electrode of a fuel cell, air supply unit (24) which supplies air to the fuel supply path, CO removal catalyst (62) which removes CO, positioned downstream the fuel-supply path of the air supply unit, measurement unit (102) which measures CO concentration contained in the fuel gas, control unit, light emission part (126) which outputs laser beam with near-infrared wavelength range including the absorption wavelength of CO, optical system, light-receiving part (124), and calculation part (130).    USE - Carbon monoxide (CO) removal system for fuel cell (claimed).    ADVANTAGE - The CO removal system and CO removal method can reduce carbon monoxide by high probability and more efficiently from fuel gas, is effective in suppressing deterioration of fuel electrode, can produce electric power stably and stably outputs electric power by predetermined performance.    DETAILED DESCRIPTION - A carbon monoxide (CO) removal system has fuel supply path (12) which supplies fuel gas to the fuel electrode of a fuel cell, air supply unit (24) which supplies air to the fuel supply path, CO removal catalyst (62) which removes CO, positioned downstream the fuel-supply path of the air supply unit, and makes CO and oxygen react, measurement unit (102) which measures CO concentration contained in the fuel gas which passed the CO removal catalyst, control unit which controls the reaction environment of CO removal catalyst based on CO concentration measured by the measurement unit, light emission part (126) which outputs laser beam with near-infrared wavelength range including the absorption wavelength of CO, optical system where laser beam in the fuel-supply path enters, light-receiving part (124) which receives the laser beam injected from the light emission part and passed through the fuel supply path, and calculation part (130) which computes the CO concentration of the fuel gas that flows through the fuel supply path based on the intensity of the laser beam output from the light emission part, and the intensity of laser beam received by the light-receiving part. An INDEPENDENT CLAIM is included for CO removal method.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the schematic structure of CO removal system. (Drawing includes non-English language text).    CO removal system (22)    Control unit (32)    Fuel electrode (46)    1st air supply part (66)    Temperature-control part (70)