NOVELTY - The reformer comprises a first oxidation catalyst provided in an ignition fuel for combustion in an upside of a burner and heated by a combustion flame that downwardly faces the burner. The first oxidation catalyst is directly emitted through a gas nozzle. A second oxidation catalyst heats an exhaust gas passing the ventilating passage to transfer the heat delivered from the heated first oxidation catalyst, and is placed in the ventilating passage in which the exhaust gas by combustion surrounds an outer periphery of an inner chamber equipped with the first oxidation catalyst.    USE - The dual combustion reformer is useful in a fuel cell system (claimed).    ADVANTAGE - The reformer is environment-friendly, enhances the reforming performance of the second oxidation catalyst thus rapidly producing hydrogen, enhances hydrogen retrieval performance of the reforming catalyst, and improves safety and marketability of the fuel cell stack.    DETAILED DESCRIPTION - The reformer comprises a first oxidation catalyst provided in an ignition fuel for combustion in an upside of a burner and heated by a combustion flame that downwardly faces the burner. The first oxidation catalyst is directly emitted through a gas nozzle. A second oxidation catalyst heats an exhaust gas passing the ventilating passage to transfer the heat delivered from the heated first oxidation catalyst, and is placed in the ventilating passage in which the exhaust gas by combustion surrounds an outer periphery of an inner chamber equipped with the first oxidation catalyst. Hydrogen is downwardly flowed in the burner so that the hydrogen is recirculated in a fuel cell stack. The ventilating passage equipped with the second oxidation catalyst passing through an inner chamber and an outer chamber. The outer chamber wraps the inner chamber. A reforming catalyst covering the second oxidation catalyst is formed at the outer chamber. An aqueous conversion catalyst surrounds the reforming catalyst. The gas nozzle is arranged in a same cord as the burner. The gas nozzle is composed of an opening part arranged according to a circumference of a nose that turns toward the second oxidation catalyst and a nose that turns toward the first oxidation catalyst. The second oxidation catalyst is expanded in an end portion of a nozzle body and downwardly located in the nozzle body of the burner that is supplied with the hydrogen. A concave type flow guider comprises a site facing the nozzle body. The gas nozzle is composed of sprayed oil drawing opening part connected in a positioner that is arranged in the opening part and turns toward the first oxidation catalyst and the second oxidation catalyst. The sprayed oil drawing opening part is connected in an end portion of the nozzle body. The positioner is screwed up with the nozzle body. An INDEPENDENT CLAIM is included for a fuel cell system.