NOVELTY - A membrane-electrode assembly has polymer electrolyte membrane (7) and two gas diffusion electrodes bonded to both surface of membrane. The gas diffusion electrode has electrode catalyst layer (5), gas diffusion layer, and intermediate layer (6) made of ion conductor between electrode catalyst layer and membrane. The ion conductor comprises polymer block (a) (1) having ion-conductive group and polymer block (b) (2) which does not have ion-conductive group, in which two blocks are made primarily from block copolymers causing phase separation from each other.    USE - Membrane-electrode assembly is used for polymer electrolyte fuel cell (claimed) used as power supply for electric vehicle and portable equipments.    ADVANTAGE - The membrane-electrode assembly provides economical and environmental friendly polymer electrolyte fuel cell having excellent electric power generation performance and favorable moldability.    DETAILED DESCRIPTION - A membrane-electrode assembly has polymer electrolyte membrane and two gas diffusion electrodes bonded to both surface of membrane. The gas diffusion electrode has electrode catalyst layer, gas diffusion layer, and intermediate layer made of ion conductor between electrode catalyst layer and membrane. The ion conductor comprises polymer block (a) having ion-conductive group and polymer block (b) which does not have ion-conductive group, in which two blocks are made primarily from block copolymers which causes phase separation from each other. The polymer (a) forms continuous phase, and bonded area between intermediate layer and membrane, and bonded area between intermediate layer and electrode catalyst layer having ion-conductive groups.    DESCRIPTION OF DRAWING(S) - The drawing shows schematic view illustrating structure of intermediate layer provided in membrane electrode assembly.    Polymer block having ion-conductive group (1)    Polymer block which does not have ion conductive group (2)    Electrode catalyst layer (5)    Intermediate layer (6)    Electrolyte membrane (7)