Abstract: A motor comprises a casing having a plurality of slots; an interior of the casing having a coil which is formed by winding enamel-insulated wires; an inner cover; an outer cover locked to the casing and the inner cover; and a rotor placed within the casing and fixed to be between the outer cover and the casing by a bearing; an inner diameter of the casing being matched to the diameter of the rotor; a very small gap being formed between the rotor and the casing so that the rotor is rotatable therein. An outer side of the casing has wavelike textures. External air is guided into the wave like textures so by the texture of the casing. Air flows along the texture so as to have predetermined heat dissipating effect, dust proof effect and water proof effect.