NOVELTY - The assembly has an anode (3), and a cathode (4) including a catalyst layer (10) that is connected with an electrolyte membrane (2) and a diffusion layer (11) sandwiching the catalyst layer with the membrane. Amount of pores at an interface between the membrane and the catalyst layer and between the diffusion and the catalyst layers contains 2 to 20 percentages of total volume of a portion between the membrane and the diffusion layer. Depth of the pores at the interface between the diffusion and the catalyst layers is equal to or less than 50 percentages of thickness of the catalyst layer.    USE - Membrane-electrode assembly for a direct oxidation fuel cell (claimed) for an automobile i.e. electric scooter, and portable small-size electronic device such as cellular phone, notebook personal computer and digital still camera.    ADVANTAGE - The assembly reduces the defect of the catalyst layer, enhances the evenness of the electrode reaction over the region of the catalyst layer, quickly increases the pressure exerted on the condensed water to a pressure for discharging the condensed water into the oxidant flow channel of the separator through the pores of the diffusion layer, and discharges condensed water accumulated in the pores into the oxidant flow channel at short intervals. The catalyst layer allows oxygen diffusibility to be maintained at a high level for long period of time, so that the amount of increasing activation over voltage with time is small. The direct oxidation fuel cell has high power density. The assembly prevents the electrode reaction of the cathode from being uneven due to large defect of the cathode catalyst layer, thus maintaining the cathode over voltage with low stability.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a direct oxidation fuel cell including a unit cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a unit cell with a membrane-electrode assembly for a direct oxidation fuel cell.    Unit cell (1)    Electrolyte membrane (2)    Anode (3)    Cathode (4)    Catalyst layer (10)    Diffusion layer (11)