A direct oxidation fuel cell is provided. A direct oxidation fuel cell includes one or more electricity generators which have a membrane-electrode assembly and anode and cathode members disposed in close contact with respective sides of the membrane-electrode assembly interposed therebetween to generate electrical energy and water by a reaction of a fuel and oxygen. The cathode member includes a plurality of air vents through which air flows and is exposed to the atmosphere. Diameters of a plurality of the air vents gradually increase in a direction toward an exposed area of the cathode member.