The direct oxidation fuel cell of the present invention is provided with: a membrane electrode assembly including an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode; an anode-side separator having a fuel flow channel for supplying fuel to the anode; and a cathode-side separator having an oxidant flow channel for supplying oxidant to the cathode, in which the anode includes an anode catalyst layer disposed at the side of the electrolyte membrane and an anode diffusion layer disposed at the side of the anode-side separator. The anode diffusion layer includes a water repellent layer disposed at the side of the anode catalyst layer and including a first conductive agent and a first water repellent agent; and a substrate layer disposed at the side of the anode-side separator, and the porosity of the substrate layer is higher at the downstream side than at the upstream side of the fuel flow.