NOVELTY - A reformation unit (300) is equipped with case component in which inner area is accommodated with modifier (620), carbon monoxide (CO)-modifying device (820), and carbon monoxide selective-oxidation device (830), and outer portion has heat insulation portion (500) in which heat insulation component (511B) of block shaped is positioned continuously. The heat insulation portion is formed along outer surface of case component. The modifier generates reformed gas containing hydrogen gas by heating source gas containing hydrocarbon raw material with combustion gas.    USE - Reformation unit is used in fuel cell system (claimed).    ADVANTAGE - The fuel cell system including reformation unit is simple in structure, and efficiently and stably performs reformation process.    DETAILED DESCRIPTION - A reformation unit is equipped with case component in which inner area is accommodated with a modifier, a carbon monoxide (CO)-modifying device, and carbon monoxide selective-oxidation device, and outer portion has a heat insulation portion in which heat insulation component of two or more approximately block shaped is positioned continuously. The heat insulation portion is formed along an outer peripheral surface of case component. The modifier generates reformed gas containing hydrogen gas by heating source gas containing hydrocarbon raw material with combustion gas of burner in presence of modification catalyst. The generated reformed gas in modifier is supplied to CO-modifying device, and converts carbon monoxide in reformed gas to carbon-dioxide in presence of CO-modifying catalyst. The CO selective-oxidation device oxidizes (CO2)CO which is processed by reformed gas, and remains in the reformed gas according to CO selective-oxidation catalyst.    DESCRIPTION OF DRAWING(S) - The drawing shows sectional side view of reformation unit in fuel cell system.    Reformation unit (300)    Heat insulation portion (500)    Heat insulation component (511B)    Modifier (620)    CO-modifying device (820)    CO selective-oxidation device (830)