PURPOSE: To contrive to lighten an apparatus without lowering its output characteristics by making a volume of a clockwise projecting part of salient pole piece arm smaller than that of a counterclockwise projecting part thereof.

CONSTITUTION: Salient pole pieces 21 and slots 22 are alternately formed in a iron core 20 of rotor R. A salient pole piece 21 is composed of a leg 21a extending radially from the central part of said iron core 20 and an arm 21b formed into a T-shape at an outer end of said leg 21a. To form said arm 21b, a counterclockwise projecting part p and a clockwise projecting part q are caused to project from the outer end of each leg 21a in the direction of rotation of the iron core 20 and reversely to said direction, respectively. The thickness of the clockwise projecting part q is thinner than that of the counterclockwise projecting part p. In this manner, the weight of an electrical rotating machine can be decreased while output characteristics of said machine are maintained appropriately.