An increase of the magnetization current can be restrained during demagnetization and magnetization, and a variable speed operation can be achieved at a high power output over a wide range of from a low speed to a high speed. A rotor 1 is configured by a rotor core 2, permanent magnets 3 having a small value as the product of the coercivity and the thickness in the magnetization direction thereof, and permanent magnets 4 having a large value as the product. When reducing a flux linkage of the permanent magnets 3, a magnetic field directed to the reverse direction of the magnetization direction of the permanent magnets 3 due to a current of an armature coil is caused to act on them. When increasing a flux linkage of the permanent magnets 3, a magnetic field directed to the same direction as the magnetization direction of the permanent magnets 3 due to a current of an armature coil is caused to act on them. A short circuit coil 8 is located in a magnetic path part of each permanent magnet 4 other than the permanent magnets 3. A magnetic field due to a magnetization current induces an induced current to generate a magnetic field on the periphery of the short circuit coil 8. The generated magnetic field and the magnetization current generate a magnetic field to magnetize the permanent magnets 3.