NOVELTY - A modifier (20) has modification zone (60) which generates reformed gas from fuel. A reaction zone (80) decreases carbon monoxide concentration from the reformed gas to preset range. A purification zone (40) further decreases the carbon monoxide concentration in the reformed gas supplied from the reaction zone.    USE - Modifier for generation of hydrogen rich reformed gas from fuel such as natural gas, liquid petroleum gas, kerosene gas, before supply to fuel cell.    ADVANTAGE - Due to the reaction zone, carbon monoxide is decreased to preset range in the purification zone, without need of excess supply of oxygen into the purification zone. Since there is no useless consumption of hydrogen, the reduction in thermal efficiency of the modifier is prevented. Thus thermal efficiency is improved by supplying reformed gas with fixed carbon monoxide concentration to the purification zone. Since the refrigerant of the modifier is used as the refrigerant of the heat exchanger, production cost is reduced.    DETAILED DESCRIPTION - A modifier (20) has modification zone (60) which generates reformed gas from fuel. A reaction zone (80) decreases carbon monoxide concentration from the reformed gas to preset range. A purification zone (40) further decreases the carbon monoxide concentration in the reformed gas supplied from the reaction zone. A controller adjusts the supply amount of refrigerant based refrigerant temperature in reaction zone. The refrigerant employed in the modifier is in liquid or gas form. The reaction zone, carbon monoxide purification zone, and the modification zone are held in order along vertical direction. A heat exchanger (91) is attached to the outer wall surface of the carbon monoxide reaction zone. Combustion and evaporation sections (50,30) are provided in the modification zone, whereas the cooling section (70) is provided in the reaction zone.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the modifier.(Drawing includes non-English language text).    Modifier (20)    Evaporation and combustion sections (30,50)    Purification zone (40)    Modification zone (60)    Reaction zone (80)    Cooling section (70)    Heat exchanger (91)