A plurality of split iron cores combined with each other to form an annular shape and having yoke portions arranged along an outer circumference of the annular shape and tooth portions protruding to an inner side in a radial direction from the yoke portions, insulators disposed at both ends in an axial direction of each split iron core, and a coil wound around each tooth portion through at least parts of the insulators, are included. The insulators have protrusions protruding from end surfaces in a circumferential direction of each yoke portion. When the coil is wound around the tooth portion, each protrusion is deformed, thereby being fixed together with the yoke portion.