A coil is made by helically winding a wire rod. A cross-sectional shape of the wire rod of the coil includes a curved portion that is arcuately curved toward a center axis of the coil； a flat portion that is provided on an outer circumference of the coil, and is formed in a flat shape with a curvature that is smaller than a curvature of the curved portion； and at least one protruding portion that is provided at the boundary between the curved portion and the flat portion or in the vicinity of the boundary, and protrudes toward an adjacent wire rod.
