To provide a manufacturing method of a membrane electrode assembly which improves the reliability of seal, mechanical strength, and handling ability of a solid polymer type fuel cell. The manufacturing method of a membrane electrode assembly according to the present invention prepares a membrane electrode assembly which differs in size of gas diffusion layers at an anode side and cathode side, provides the outer peripheral edge of the membrane electrode assembly with a resin frame by molding, and, at that time, provides projections or a concave part and convex part at a top mold and bottom mold used for the molding so as to keep to a minimum the penetration of the resin frame material to the gas diffusion layers and/or electrode layers and prevent warping of the outer peripheral edges of the larger gas diffusion layer etc.