The present invention provides a method for manufacturing 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 includes: preparing a membrane electrode assembly which differs in the size of the gas diffusion layers at the anode side and the cathode side; and providing a resin frame at the outer peripheral edge of the membrane electrode assembly by molding; wherein the molding includes the use of a mold that keeps penetration of the resin frame material into the gas diffusion layers and/or electrode layers to a minimum and prevents warping of the outer peripheral edges.