A motor includes a base, a stator, a retaining seat, a bearing, a retaining ring and a rotor. The base has a shaft tube with an assembling hole. The stator is mounted around the shaft tube. The retaining seat, bearing and retaining ring are received in the assembling hole. Outer diameters of the retaining seat and the retaining ring are equal to a diameter of the assembling hole. The bearing is sandwiched and positioned between the retaining ring and the retaining seat. Radial and axial movement of the retaining seat, the bearing and the retaining ring is avoided effectively after being mounted into the shaft tube, so that the rotor is smoothly coupled to the retaining ring, the nearing and the retaining seat. Consequently, convenience of assembling and a simplified structure are provided.