there is provided a winding to be wound at a stator of a rotary electric machine . the winding is produced from a flat wire having a rectangular cross section along a plane perpendicular to a length - wise direction . the flat wire is coated with an electric insulating layer and is bent to have curves at given portions of the flat wire in the length - wise direction . the curves are located on an axial outer side of the stator . the cross section of the flat wire has four corners , among which mutually - adjacent two corners are lager in curvatures than remaining mutually - adjacent two corners . the mutually - adjacent two corners whose curvatures are smaller are positioned on a circumferential outer side of each of the curves and the mutually - adjacent two corners whose curvatures are larger are positioned on a circumferential inner side of each of the curves .