Supposing a straight line joining rotation center O of a rotor and a magnetic pole middle, that is, a middle of permanent magnets (25) to be a d-axis, and a straight line joining rotation center O and an intermediate point of mutually adjacent permanent magnets (25) to be a q-axis, mutually adjacent arcs A1 and A2 are composed such that radius R1 of arc A1 at the d-axis side is larger than radius R2 of arc A2 at the q-axis side, and that, at intersection point β of mutual arcs A1 and A2, angle α of tangent u of arc A2 at the q-axis side with respect to tangent t of arc A1 at the d-axis side is set by −3 degrees≦α≦2 degrees.