A rotor of an outer rotor type motor is coupled to an outside of a stator, and is provided with a shaft coupler, for being connected with a shaft of a drum, fixed at its center portion by an injected material, and a plurality of radiation holes formed therein continuously in a radial direction. The rotor includes at least one cooling fin provided with a base member fixed to a bottom surface of the rotor and a curved member attached to the base member, wherein the cooling fin is combined with the bottom surface so as to be disposed adjacent to the radiation hole. Therefore, a contact area with air can be increased, and an air circulation through the radiation holes can be facilitated. Accordingly, deterioration of the efficiency of a washing machine is prevented despite long periods of operation, and any damage caused by overheating is prevented.