A permanent-magnet motor comprising: a stator provided with a stator core having a plurality of teeth and a plurality of slots and an armature winding having a plurality of multiphase windings that are wound around the teeth and are contained in the slots; and a rotor provided with a rotor core facing the stator core via a predetermined air gap, a plurality of permanent magnets embedded in the rotor core, and a plurality of magnetic-field poles, wherein the plurality of permanent magnets form a plurality of permanent-magnet pairs arranged symmetrically about a center axis of the rotor core, wherein in each of the permanent-magnet pairs, the permanent magnets are arranged symmetrically with respect to a radial-direction straight line intersecting the center axis of the rotor core, wherein end surface portions of the permanent magnets having a different polarity substantially face each other, wherein each of the permanent-magnet pairs is configured with a pair of the permanent magnets that are arranged in a v-shaped manner in such a way that the distance between the portions of the permanent magnets, facing each other at the outer side in the radial direction of the rotor core, is smaller than the distance between the portions thereof, facing each other at the inner side in the radial direction of the rotor core, and wherein each magnetic-field pole is formed of a part of the rotor core that is situated between two adjacent permanent magnets of two adjacent permanent-magnet pairs; characterized in that: when it is assumed that R denotes the length of the outer circumference of the rotor core, Wc denotes the circumferential-direction maximum width, between the permanent magnets defining each of the foregoing magnetic-field poles, of the rotor, Lc denotes the axial-direction length of each permanent magnet, Wm denotes the length of each permanent magnet in a direction perpendicular to the axial direction, and W denotes the total weight of the permanent magnets for forming one magnetic-field pole, the rotor is formed in such a way as to satisfy the equation below: − 30.3 × W / Lc + 89 − 1.3 ≦ Wc × R / Wm ≦ − 30.3 × W / Lc + 89 + 1.3, wherein R, Wc, Lc and Wm are expressed in mm and W is expressed in g. a stator provided with a stator core having a plurality of teeth and a plurality of slots and an armature winding having a plurality of multiphase windings that are wound around the teeth and are contained in the slots; and a rotor provided with a rotor core facing the stator core via a predetermined air gap, a plurality of permanent magnets embedded in the rotor core, and a plurality of magnetic-field poles, wherein the plurality of permanent magnets form a plurality of permanent-magnet pairs arranged symmetrically about a center axis of the rotor core, wherein in each of the permanent-magnet pairs, the permanent magnets are arranged symmetrically with respect to a radial-direction straight line intersecting the center axis of the rotor core, wherein end surface portions of the permanent magnets having a different polarity substantially face each other, wherein each of the permanent-magnet pairs is configured with a pair of the permanent magnets that are arranged in a v-shaped manner in such a way that the distance between the portions of the permanent magnets, facing each other at the outer side in the radial direction of the rotor core, is smaller than the distance between the portions thereof, facing each other at the inner side in the radial direction of the rotor core, and wherein each magnetic-field pole is formed of a part of the rotor core that is situated between two adjacent permanent magnets of two adjacent permanent-magnet pairs; characterized in that: when it is assumed that R denotes the length of the outer circumference of the rotor core, Wc denotes the circumferential-direction maximum width, between the permanent magnets defining each of the foregoing magnetic-field poles, of the rotor, Lc denotes the axial-direction length of each permanent magnet, Wm denotes the length of each permanent magnet in a direction perpendicular to the axial direction, and W denotes the total weight of the permanent magnets for forming one magnetic-field pole, the rotor is formed in such a way as to satisfy the equation below: − 30.3 × W / Lc + 89 − 1.3 ≦ Wc × R / Wm ≦ − 30.3 × W / Lc + 89 + 1.3, wherein R, Wc, Lc and Wm are expressed in mm and W is expressed in g.