With a spindle motor, a stator core comprises a plurality of salient pole portions that are formed in a radial shape, are wound with a stator coil, and are disposed at a uniform angle except for a non-equiangular pitch region, a circular outer peripheral yoke formed so as to be continuous with the outer peripheral side of the salient pole portions, a cut-out which is formed by cutting out part of the outer peripheral yoke in an approximate sector-shape except in the non-equiangular pitch region of the salient pole portions, and a compensating pole plate which is provided in the cut-out along the ends on the inner peripheral side of the non-equiangular pitch region where the salient pole portions are formed.