A core segment sub-assembly has a first holding groove, which holds a start part of a coil wire of a three-phase winding, and a second holding groove, which holds an end part of the coil wire of the three-phase winding, at positions on an axial end surface of an annular covering part and shifted in a circumferential direction relative to a tooth covering part, on which the winding is provided. The first holding groove and the second holding groove sandwiches the tooth covering part and are separated more from each other as extending in a radially outward direction. The positions and the directions of the first holding groove and the second holding grooves are matched to the paths of the coil wire wound by a flyer type winding machine. The stator can thus be made suited to a winding process by the flyer type winding machine.