An electric rotating machine comprising a rotor having a plurality of permanent magnets arranged at an outer peripheral portion of a rotor main body, and a stator arranged outward of the rotor main body in a radial direction of the rotor main body, the stator comprising a plurality of tooth portions arranged at predetermined intervals in a circumferential direction of the rotor; a stator yoke portion arranged outside of the plurality of tooth portions; and a magnetic resistance changing mechanism configured to change a magnetic resistance of a stator magnetic path, which is formed by the stator yoke portion and each of the plurality of tooth portions, by mechanically changing the stator magnetic path; wherein each of the plurality of tooth portions includes a pair of side protruded portions (31a, 31a) protruding from both sides of a rotor side end portion of each of the plurality of tooth portions in the circumferential direction; wherein a magnetic resistance of a magnetic path formed by a gap between a pair of adjacent side protruded portions (31a, 31a) of a pair of adjacent tooth portions has a value so that when the magnetic resistance changing mechanism is in a first state in which the stator magnetic path is changed so that the magnetic resistance of the stator magnetic path is minimum or near minimum, a main magnetic path that extends from one of the magnetic poles of one of a pair of adjacent permanent magnets is formed by a magnetic path passing substantially through the pair of adjacent tooth portions corresponding to the pair of adjacent permanent magnets and the stator yoke portion; and when the magnetic resistance changing mechanism is in a second state in which the stator magnetic path is changed so that the magnetic resistance of the stator magnetic path is maximum or near maximum, the main magnetic path is formed by a magnetic short-path passing substantially through a rotor side end portion of the tooth portion; wherein in a first relative position in which adjacent end portions of the pair of adjacent permanent magnets are positioned corresponding to a circumferential intermediate portion of the rotor side end portion of each tooth portion, a first magnetic short-circuit C1 is a magnetic short-circuit C including a magnetic short-path passing substantially through the circumferential intermediate portion; wherein in a second relative position in which adjacent end portions of the pair of adjacent permanent magnets are positioned corresponding to one of circumferential end portions of the rotor side end portion of each tooth portion, a second magnetic short-circuit C2 is a magnetic short-circuit C including a magnetic short-path passing substantially through the one of circumferential end portions; wherein in a third relative position in which adjacent end portions of the pair of adjacent permanent magnets are positioned corresponding to a pair of adjacent side protruded portions (31 a, 31 a), a third magnetic short-circuit C3 is a magnetic short-circuit C including a magnetic short-path passing substantially through the gap between the pair of adjacent side protruded portions (31a, 31a); characterized in that when the magnetic resistance changing mechanism is in the second state, the second magnetic short-circuit C2 has a total magnetic resistance between a total magnetic resistance of the first magnetic short-circuit C1 and a total magnetic resistance of the third magnetic short-circuit C3, and is configured to control a change ratio of the total magnetic resistance of the magnetic short-circuit C when the magnetic short-circuit C is changed from the second magnetic short-circuit C2 to the third magnetic short-circuit C3 and from the third magnetic short-circuit C3 to the second magnetic short-circuit C2 in accordance with a relative rotational movement of the rotor with respect to the stator. when the magnetic resistance changing mechanism is in a first state in which the stator magnetic path is changed so that the magnetic resistance of the stator magnetic path is minimum or near minimum, a main magnetic path that extends from one of the magnetic poles of one of a pair of adjacent permanent magnets is formed by a magnetic path passing substantially through the pair of adjacent tooth portions corresponding to the pair of adjacent permanent magnets and the stator yoke portion; and when the magnetic resistance changing mechanism is in a second state in which the stator magnetic path is changed so that the magnetic resistance of the stator magnetic path is maximum or near maximum, the main magnetic path is formed by a magnetic short-path passing substantially through a rotor side end portion of the tooth portion;