A gas diffusion layer-integrated gasket 1 includes a first gasket 12 which is integrally molded to a periphery of a first gas diffusion layer 11 and a second gasket 14 which is integrally molded to a periphery of a second gas diffusion layer 13, and a hinge part 15 which connects the first gasket 12 and second gasket 14 to each other. The first and second gas diffusion layers sandwich a membrane-electrode assembly 2 in which catalytic electrode layers are provided on both surfaces of an electrolytic membrane from both sides, wherein a seal protrusion 12c is formed on a surface which is in tight contact with the membrane-electrode assembly 2.