A stator of an electric motor comprises: a stator core (9) with en even number of radially extending teeth (10) comprising slots (12) therebetween; an insulator (11) covering the teeth(10); and coils (13) wound around teeth (10). The insulator (11) comprises guide projections (11a) one corresponding to every tooth (10) so as to guide the coil wire (14). The guide projections (11a) comprises guide sections (11d), including a base end part (11b) and a front end part (11c). In each of the guide sections (11d), the radial thickness of at least a part of the base end part (11b) is thinner than the radial thickness of the front end part (11d). The guide sections (11d) are formed on same radial side surfaces than the guide projections (11a).
