An electric rotating machine includes a stator, a rotor inserted in a bore of the stator such that an air gap is formed between the stator and the rotor, and a plurality of permanent magnets embedded in a peripheral portion of the rotor core of the rotor in a circumferential arrangement. Slits are formed in portions of the rotor core each extending between the adjacent magnetic poles. Compressive stress is induced in portions of the rotor core each extending between the slit and the permanent magnet when stress is induced in the portion of the stator core extending between the slit and the permanent magnet by centrifugal force produced when the rotor rotates and acting on the permanent magnet and a pole piece covering the permanent magnet.