A stator assembly is provided and includes a laminated core and a one-part insulator having cover walls for covering edges of the laminated core, wherein first projections and a second projection both having a height smaller than the difference between the height of the cover walls and the thickness of the laminated core are formed on one side surface of the insulator in such a manner as to make contact with a part of one axial end side surface of the laminated core, whereby a gap which corresponds to the projection distance of the first and second projections and which serves as a clearance space for chips scraped by the edges of the laminated core from the surfaces of the cover walls is provided between the insulator and the laminated core, resulting in ensuring that the insulator is snap-fitted on the laminated core in good shape.