A complementary permanent magnet structure capable of minimizing the cogging torque for a rotating electric machine, the complementary permanent magnet structure comprising: a magnetic pole core being cylinder shaped with even numbered arc-shaped magnetic sets positioned with equal distances on the circumference thereof, each magnetic set being composed of a first permanent magnet unit and a second permanent magnet unit; and an armature core being ring shaped with a plurality of slots; wherein the ratio of the number of the slots to the number of magnetic poles of the magnetic pole core is 3/2; wherein the first permanent magnet unit and the second permanent magnet unit are positioned correspondingly to generate two complementary cogging torques with 180 degrees of electrical angle difference.