NOVELTY - A modifier (1) comprises catalyst unit (10) containing modification catalyst (2) which modifies hydrogen-type fuel which contains hydrogen as structural component and produces hydrogen and oxidation catalyst (3) which is positioned in upstream and oxidizes under oxygen environment, outer jacket case (4) which accommodates catalyst unit, entrance part (5) which takes in hydrogen-type fuel as mixed gas with air from upstream channel (8), and exit part (6) which discharges generated reformed gas to downstream channel (9). Outer jacket case is provided with outer peripheral wall part (7).    USE - A modifier for reforming hydrogen-type fuel and producing hydrogen (all claimed) used in fuel cell.    ADVANTAGE - Uniform heating can be achieved, and production of thermal radiation from oxidation catalyst and modification catalyst to external air can be suppressed.    DETAILED DESCRIPTION - A modifier (1) comprises catalyst unit (10) containing modification catalyst (2) which modifies hydrogen-type fuel which contains hydrogen as structural component and produces hydrogen and oxidation catalyst (3) which is positioned in upstream and oxidizes under oxygen environment, outer jacket case (4) which accommodates catalyst unit, entrance part (5) which takes in hydrogen-type fuel as mixed gas with air from upstream channel (8), and exit part (6) which discharges generated reformed gas to downstream channel (9). Outer jacket case is provided with outer peripheral wall part (7) which surrounds outer periphery of modification catalyst and oxidation catalyst, in which heat insulating material (11) is positioned on inner wall of outer peripheral wall part of outer jacket case. Metal tape (12) is positioned on outer periphery of oxidation catalyst and modification catalyst and is positioned between oxidation catalyst and modification catalyst and heat insulating material.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the modifier.    Modifier (1)    Modification catalyst (2)    Oxidation catalyst (3)    Outer jacket case (4)    Entrance part (5)    Exit part (6)    Outer peripheral wall part (7)    Upstream channel (8)    Downstream channel (9)    Catalyst unit (10)    Heat insulating material (11)    Metal tape (12)