NOVELTY - The method involves positioning a porous gas diffusion layer (20) in thickness direction at both sides of a membrane electrode composite body (11). A pair of electrode layers is provided on both surfaces of an electrolytic membrane. An electric power generation body (10) is provided with another porous gas diffusion layer (12). A filling part (20c) is formed along a position adjacent to edge parts (12a, 20a) by impregnating a liquid rubber-type material. The former gas diffusion layer (20) is set in a metal mold (40). An inner surface of the metal mold is filled with a liquid molding material.    USE - Method for manufacturing a seal structure body (claimed) for a fuel cell.    ADVANTAGE - The gasket is firmly joined through an impregnation part to both of the gas diffusion layers, so that simple seal structure body for fuel cells can be obtained. The filling part can restrict the impregnation of the molding material, thus effectively preventing an electric power generation area from narrowing by expansion of the impregnation part. The generation of the burr to the surface of the former gas diffusion layer can be prevented. The bad influence to the electric power generation function by volatilization gas and elution gas from the gasket can be prevented. The unnecessary expansion of the impregnation part is prevented, thus ensuring required electric power generation area.    DETAILED DESCRIPTION - The rubber-type material is selected from liquid silicone rubber, liquid fluorine type rubber and a liquid ethylene propylene rubber. An INDEPENDENT CLAIM is also included for a seal structure body for a fuel cell comprising a gas diffusion layer.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic illustration of a method for manufacturing a seal structure body for a fuel cell.    Electric power generation body (10)    Membrane electrode composite body (11)    Porous gas diffusion layers (12, 20)    Edge parts (12a, 20a)    Filling part (20c)    Metal mold (40)