At least part of each bridge portion is heated and molten to form a keyhole, and a nonmagnetic element is disposed around the keyhole. Thus, even when the width of the bridge portion in the radial direction is increased, the bridge portion is demagnetized. Therefore, leakage flux in the bridge portion is reduced, and the output power of a motor is increased. Moreover, by increasing the width of the bridge portion in the radial direction, the strength of the bridge portion is increased, and breakage of the bridge portion due to a centrifugal force at high-speed rotation of a rotor is prevented.