NOVELTY - A composite material for hydrogen separation by selective permeation of hydrogen in a gas comprises a porous support and a hydrogen-separating metal carried on such support, in which the hydrogen-separating metal is so carried on the support as to block its pores within it.    USE - The device is reforming fuel gas with separation of hydrogen for fuel cells.    ADVANTAGE - Such device has improved performance capability for hydrogen separation and size miniaturization.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for;    (1) A similar composite material in which the metal is simply carried in the pores;    (2) A method for making the composite material by mixing the porous support and hydrogen-separating metal in a solution to precipitate the product, or by forming a paste for sintering; or by mixing the porous support-producing microparticles with an organic solvent, molding into shape for sintering, and applying the hydrogen-separating metal into the pores; or by filling the hydrogen-separating metal into pores of the support for sintering; or by filling a hydrogen-separating metal into pores of a porous support, packing a catalyst suitable for chemical reaction in producing a hydrogen-containing mixed gas from a specific raw material into pores of another support and fusing the prepared supports into a unit; or by mixing, or impregnating, particles of the catalyst and/or hydrogen-separating metal, e.g. in a solvent, into pores of the support before molding into shape evenly or with deviation is distribution towards the thickness direction;    (3) A fuel gas-forming device made with the composite material to produce a hydrogen-rich fuel gas from a specific raw material, which optionally comprises a mixed gas supply part, extraction part and pressure-adjusting means; or uses a specific material for fuel gas in fuel cell with a chemical reaction part and transportation means; and    (4) A low or high-temperature type fuel cell system using the fuel gas produced by the composite material for power generation.