An arm of a coil segment having an approximate U shape is placed in a slot of a stator core, and a portion protruding from the slot is bent in a circumferential direction. An arm is bent in a direction of an arrow A, and another arm positioned at an inner side in the radial direction in relation to this arm is bent in a direction of an arrow B. The arm positioned at the outer side has at least a part of a bending inner side surface of a bent portion hardened by pressurization.