Disclosed is a membrane electrode assembly for solid polymer fuel cells which is excellent in dimensional stability and mechanical strength and exhibits high durability during power generation. Also disclosed is a solid polymer fuel cell. Specifically, a solid polymer electrolyte membrane (111, 211, 311) comprises a region 1 which has proton conductivity throughout the thickness direction of the membrane and a region 2 which is located around the region 1 and does not have proton conductivity throughout the thickness direction of the membrane due to an imperforate sheet arranged therein. Catalyst layers (127, 128) are so arranged that the outer peripheries are within the region 2.