In a stepping motor in which a cylindrical magnet which is magnetized in an axial direction is coupled with a rotary shaft and the magnet is clamped with rotor stacks formed by laminating annular magnetic plates, the surfaces of which are electrically insulated, to form a rotor, and around the outer circumference of the rotor stator cores which are wound with stator coil are disposed, a sleeve is pressed in between the magnet and the rotor stacks, and the rotary shaft and interposed therebetween. The cutting operation for the outer diameter of the rotor during the manufacturing processes is carried out while holding both ends of the sleeve, subsequently, the rotary shaft is inserted, thereby, regardless of the length of the rotary shaft, the manufacturing processes are carried out to reduce the number of the molds.