NOVELTY - The membrane electrode assembly (13) comprises an electrolyte membrane (10), an anode (11) disposed on a face of the membrane, and a cathode (12) disposed on the other face of the membrane. The cathode includes a cathode catalyst layer (18) with a first main surface and a second main surface. The cathode catalyst layer includes a cathode catalyst, a polymer electrolyte, and first and second regions. The first and second regions are different in polymer electrolyte content. The electrolyte content in each of the second regions is lower than the electrolyte content in each of the first regions.    USE - The membrane electrode assembly is useful in a unit cell for a direct oxidation fuel cell (claimed), which is useful as a power source for portable, small-sized electronic devices such as cell phones, notebook personal computers and digital still cameras, electric scooters and automobiles.    ADVANTAGE - The membrane electrode assembly has good power generation performance, high stability and durability and excellent properties such as proton conductivity, heat resistance and chemical stability, and prevents the leakage of the fuel, oxidant and reaction products.    DETAILED DESCRIPTION - The membrane electrode assembly (13) comprises an electrolyte membrane (10), an anode (11) disposed on a face of the membrane, and a cathode (12) disposed on the other face of the membrane. The cathode includes a cathode catalyst layer (18) with a first main surface and a second main surface. The cathode catalyst layer includes a cathode catalyst, a polymer electrolyte, and first and second regions. The first and second regions are different in polymer electrolyte content. The electrolyte content in each of the second regions is lower than the electrolyte content in each of the first regions. The second regions are continuous from the first main surface of the cathode catalyst layer to the second main surface along a line slanted at a predetermined angle with respect to the thickness direction of the cathode catalyst layer. The cathode catalyst layer comprises thin layers accumulated in the thickness direction. Each of the thin layers includes one of the first regions and one of the second regions. Each of the first regions included in one of the thin layers is partially in contact with each of the second regions included in an adjacent one of the thin layers. The second regions included in the thin layers are disposed in a zigzag from the first main surface to the second main surface. The first regions and the second regions are disposed regularly in the thickness direction of the cathode catalyst layer or the direction perpendicular to the thickness direction. The first regions are discontinuously disposed in the thickness direction of the cathode catalyst layer. The first regions are continuous from the first main surface of the cathode catalyst layer to the second main surface. The cathode catalyst is loaded on conductive carbon particles. The weight ratio A of the polymer electrolyte to the conductive carbon particles in each of the first regions is 0.5-0.7, and the weight ratio B of the polymer electrolyte to the conductive carbon particles in each of the second regions is 0.3-0.5. The difference between the weight ratio A and the weight ratio B is greater than or equal to 0.1. The cathode is a laminate of the cathode catalyst layer and a cathode diffusion layer (19) including a conductive porous substrate. The cathode catalyst layer is disposed to contact the electrolyte membrane. An INDEPENDENT CLAIM is included for a unit cell for a direct oxidation fuel cell.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of a unit cell included in a direct oxidation fuel cell.    Electrolyte membrane (10)    Anode (11)    Cathode (12)    Membrane electrode assembly (13)    Anode catalyst layer (16)    Cathode catalyst layer (18)    Cathode diffusion layer. (19)