A reformation unit and a fuel cell system containing the reformation unit are provided to improve reforming performance and to enhance the reducing efficiency of carbon monoxide. A reformation unit(200) comprises a fuel mixer(220) which mixes fuel and vapor uniformly; a reformer(230) which reforms the fuel and vapor discharged from the fuel mixer to generate the reformed gas; a warm water reactor(240) which reacts the carbon monoxide contained in the reformed gas discharged from the reformer with water to reduce the concentration and is provided with a catalyst part for maintaining temperature to be constant for smooth reaction; and a partial oxidation reactor(250) which reacts the carbon monoxide contained in the reformed gas discharged from the warm water reactor with air to reduce the concentration of carbon monoxide further and is provided with a reaction zone.
