To provide a composite membrane in which a mechanical strength of an ion exchange resin composed of tetrafluoroethylene copolymer is improved without spoiling proton conductivity, and which is superior in power generation characteristics and anti-methanol permeability or the like.

(1) Joining sulfonated polyarylene ether based copolymer membrane having heat resistance and mechanical characteristic and a tetrafluoroethylene copolymer membrane, (2) joining both faces of the sulfonated polyarylene ether based copolymer membrane by the tetrafluoroethylene copolymer membrane, and (3) joining both faces of the tetrafluoroethylene copolymer membrane by the sulfonated polyarylene ether based copolymer membrane are carried out, and after a phosphate based compound having at least one or more of N-vinylpyrrolidone and polymerizable unsaturated group is added onto the joined surfaces of the respective membranes, they are laminated, heated, joined, and this composite membrane is manufactured.

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