NOVELTY - A fuel treatment device (100) comprises an inner cylinder (110) with a bottom, an intermediate cylinder (120) without a bottom which surrounds the inner cylinder, an outer cylinder (130), a heating unit (115) disposed within the inner cylinder, an evaporation unit (210) which generates mixed gas by mixing steam and raw material gas containing methane, a reformation unit (220) which changes the mixed gas to reformed gas by steam-reforming reaction, and a carbon monoxide removal unit (320) which removes carbon monoxide from reformed gas.    USE - Fuel treatment device used for manufacturing fuel in fuel cell system e.g. domestic cogeneration system.    ADVANTAGE - The fuel treatment device has high durability.    DETAILED DESCRIPTION - A fuel treatment device comprises an inner cylinder with a bottom, an intermediate cylinder without a bottom which surrounds the inner cylinder, and an outer cylinder with a bottom which surrounds the intermediate cylinder. The outer cylinder comprises lower portion having a small bore diameter and including the bottom of the outer cylinder, upper portion having a bore diameter larger than that of the lower portion and including the end on the side opposite from the bottom of the outer cylinder, and the intermediate portion connecting the lower portion with the upper portion of the outer cylinder. The intermediate portion of the outer cylinder and the lower portion of the outer cylinder do not comprise an all-around welded portion. The fuel treatment device comprises a heating unit disposed within the inner cylinder, an evaporation unit which is formed between the upper portion of the inner cylinder and that of the intermediate cylinder and generates mixed gas by mixing steam and raw material gas containing methane, a reformation unit which is formed between the lower portion of the inner cylinder and that of the intermediate cylinder and changes the mixed gas to reformed gas by steam-reforming reaction, and a carbon monoxide removal unit which is formed between the upper portion of the intermediate cylinder and that of the outer cylinder and removes carbon monoxide from the reformed gas.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of fuel treating apparatus. (Drawing includes non-English language text)    Fuel treatment device (100)    Inner cylinder (110)    Heating unit (115)    Intermediate chamber (120)    Outer cylinder (130)    Evaporation unit (210)    Reformation unit (220)    Carbon monoxide removal unit (320)