A synchronous motor 100 which comprises: a stator core 1 in which a plurality of electromagnetic steel sheets, punched into a specific shape, are laminated in the axial direction; and a cylindrical permanent magnet 2 having a plurality of magnetic poles formed at the outer peripheral surface thereof and having polar anisotropy corresponding to the number of magnetic poles. The length of the permanent magnet 2 in the axial direction is greater than the length of the stator core 1 in the axial direction. Grooves 2a1 extending in the axial direction are formed in the outer peripheral surface of the permanent magnet 2 and only at one side in the axial direction of portions opposing the stator core 1 and portions not opposing the stator core 1, said grooves being formed at regular intervals in the rotation direction between magnetic poles A.
