NOVELTY - The composite membrane (12) comprises a substrate having openings, and membrane electrode assemblies disposed in the openings. Each assembly includes an electrolyte membrane having ionomer, an anode catalyst layer provided on one face of the membrane, and a cathode catalyst layer provided on the other face of the membrane. The substrate has an insulating region to insulate a periphery of the assembly, and a conducting region to electrically connect the anode catalyst layer provided on the one face of the adjacent membrane electrode assembly to the cathode catalyst layer.    USE - The composite membrane is useful in a fuel cell (claimed), which is useful for space applications, automobiles, mobile devices such as cell phones, notebook-size personal computers, personal digital assistants, MP3 players, digital cameras, electronic dictionaries or electronic books, and large and small scale power generation.    ADVANTAGE - The composite membrane can be simply, safely and efficiently manufactured with high reliability thus improving the high power generation efficiency of the fuel cell and reducing the emission of nitrogen compounds in the environment.    DETAILED DESCRIPTION - The composite membrane (12) comprises a substrate having openings, and membrane electrode assemblies disposed in the openings. Each assembly includes an electrolyte membrane having ionomer, an anode catalyst layer provided on one face of the membrane, and a cathode catalyst layer provided on the other face of the membrane. The substrate has an insulating region to insulate a periphery of the assembly, a conducting region to electrically connect the anode catalyst layer provided on the one face of the adjacent membrane electrode assembly to the cathode catalyst layer provided on the other face of the electrode assembly, where an electric conductivity and a graphitization degree of the substrate increase continuously from the insulating region towards the conducting region, and a current-collecting region provided in a surface layer portion of the substrate in contact with the anode catalyst layer or the cathode catalyst layer of the membrane electrode assemblies. The current-collecting region is electrically connected to the conducting region, where the electric conductivity of the substrate increases continuously from the insulating region towards the current-collecting region. The membrane electrode assemblies are disposed linearly in the openings of the substrate and connected in series with each other, which belong to first and second rows, where the second row is disposed in parallel with the first row. One of the conducting regions connects a first membrane electrode assembly positioned at an end of the membrane electrode assemblies belonging to the first row to a second membrane electrode assembly positioned at an end of the membrane electrode assemblies and positioned counter to the first membrane electrode assembly belonging to the second row in series with each other. The insulating region is formed of aromatic polymer such as polyimide that is graphitized by heat. An INDEPENDENT CLAIM is included for a fuel cell having a composite membrane.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross-sectional view of a fuel cell.    Fuel cell (10)    Composite membrane (12)    Anode housing (40)    Cathode housing (42)    Sealing members. (50)