In order to provide an membrane electrode assembly having an electrolyte membrane in which bending and warping of a solid polymer electrolyte membrane are prevented so as to facilitate the handling ability, in the membrane electrode assembly having an electrolyte membrane comprising a solid polymer electrolyte membrane, and a pair of gas diffusion electrodes which are disposed on both sides of the solid polymer electrolyte membrane, a flat surface having the same size as the solid polymer electrolyte membrane is formed by disposing a frame-shaped seal member on an outer surface of the gas diffusion electrode, and the flat surface closely contacts to the solid polymer electrolyte membrane so as to be able to cover and support the solid polymer electrolyte membrane.