NOVELTY - The fuel treatment apparatus comprises an air/fuel mixture chamber (7) for the formation and treatment of a mixture of fuel and a component, a reformer (8) for converting the mixture of fuel and the component into a synthesis gas, and a desulfurization unit (9) for the removal of sulfur from the synthesis gas or from the mixture. The reformer and the desulfurization unit: are disposed adjacent to each other in a housing (10) along a longitudinal axis of the housing; comprise a coated metal-support body; have a cross-section geometry; and are integrated in a one-piece unit.    USE - The fuel treatment apparatus is useful in a fuel cell system arranged in a motor vehicle for converting a hydrocarbon-containing fuel into a fuel for a fuel cell (claimed).    ADVANTAGE - The fuel treatment apparatus can be economically and easily manufactured with reduced size and lightweight.    DETAILED DESCRIPTION - The fuel treatment apparatus comprises an air/fuel mixture chamber (7) for the formation and treatment of a mixture of fuel and a component, a reformer (8) for converting the mixture of fuel and the component into a synthesis gas, and a desulfurization unit (9) for the removal of sulfur from the synthesis gas or from the mixture. The reformer and the desulfurization unit: are disposed adjacent to each other in a housing (10) along a longitudinal axis of the housing; comprise a coated metal-support body; have a cross-section geometry; and are integrated in a one-piece unit. The air/fuel mixture chamber is arranged at the reformer or at the desulfurization unit in the housing along the longitudinal axis of the housing. The metal-support body comprises a shaft structure, and is made of metal foam. The air/fuel mixture chamber, the reformer and/or the desulfurization unit comprise an electrical heating device. The desulfurization unit comprises an adsorbent for adsorptive desulfurization of sulfur from the synthesis gas. INDEPENDENT CLAIMS are included for:    (1) a fuel cell system in a motor car;    (2) a method for converting a hydrocarbon-containing fuel into a fuel for a fuel cell; and    (3) a method for treating a hydrocarbon-containing fuel.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a fuel cell system.    Fuel cell (3)    Air/fuel mixture chamber (7)    Reformer (8)    Desulfurization unit (9)    Housing. (10)