NOVELTY - A reformer for reforming a raw fuel containing hydrocarbon to produce a reformed gas comprises reforming units (106, 108) stacked together. A raw fuel channel (120) is provided in the reforming units for allowing the raw fuel to flow in a serpentine pattern in a stacking direction of the reforming units. A single layer of reforming catalysts (118) is provided in each reforming unit. The reforming catalysts are supported between an end of one of adjacent reforming units and an end of the other reforming unit in the stacking direction.    USE - For reforming a raw fuel containing hydrocarbon to produce a reformed gas (claimed).    ADVANTAGE - The raw fuel channel is formed in the reforming units for allowing the raw fuel to flow in the serpentine pattern in the stacking direction of the reforming units. The length of the raw fuel channel is increased effectively. Improvement in the reforming efficiency is achieved even if the reforming units have a compact structure. The reforming catalysts are suitably supported between the adjacent reforming units. The raw fuel flows uniformly and reliably contacts the reforming catalysts. The reforming catalysts contact the ends of the reforming units and heat is smoothly conducted to the reforming catalysts. As a result, significant temperature differences do not occur among the reforming catalysts provided in the center and outer of the reforming units. Non-uniform distribution of the reforming reaction does not occur. Since the raw fuel flows uniformly, the temperature distribution in the reforming catalysts is uniform. It is not necessary to specially determine the steam/carbon (S/C) ratio for the portion having the high temperature. A small value for the S/C ratio of the reforming unit can be used. The amount of water vapor is reduced effectively and improvement in the reforming efficiency is achieved.    DESCRIPTION OF DRAWING(S) - The figure shows a partial cross-sectional view of a reformer.    Reforming units (106, 108)    First receiver component (110)    Wall surfaces (110a, 112b)    Second receiver component (112)    First hole (114)    Second holes (116)    Reforming catalysts (118)    Raw fuel channel (120)