NOVELTY - A membrane electrode structure (1) comprises proton-conductive film (2), electrode catalyst layers (3a,3b) arranged on both surfaces of proton-conductive film, gas diffusion layers (4a,4b) arranged on electrode catalyst layers, and intermediate layers (5a,5b) arranged between electrode catalyst layer(s) and gas diffusion layer(s), which comprises noble metal nanoparticles (51), electrode electrolyte (52) and carbon powder. The electrode catalyst layers comprise catalyst particles and electrode electrolyte. The gas diffusion layers comprise porous base material.    USE - Membrane electrode structure is used for solid polymer fuel cell (claimed) for electric vehicle and mobile device.    ADVANTAGE - The membrane electrode structure has high initial performance and durability, without deterioration, and destabilization of power generation performance even when the humidity conditions around the electrodes are altered.    DETAILED DESCRIPTION - A membrane electrode structure comprises proton-conductive film which conduct protons, electrode catalyst layers arranged on both surfaces of the proton-conductive film, gas diffusion layers arranged on the electrode catalyst layers, and intermediate layers arranged between electrode catalyst layer(s) and gas diffusion layer(s). The electrode catalyst layers comprise catalyst particles and electrode electrolyte. The gas diffusion layers comprise porous base material. The intermediate layers comprise noble metal nanoparticles, electrode electrolyte and carbon powder. The thickness of intermediate layers is 2-6 mu m. An INDEPENDENT CLAIM is included for solid polymer fuel cell.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic cross-sectional view of membrane electrode structure. (Drawing includes non-English language text)    Membrane electrode structure (1)    Proton-conductive film (2)    Electrode catalyst layers (3a,3b)    Gas diffusion layers (4a,4b)    Intermediate layers (5a,5b)    Noble metal nanoparticles (51)    Electrode electrolyte (52)