First and second wires form a wire assembly by being wound around a winding core portion together. The wire assembly includes a twisted wire portion, an inner layer portion, an outer layer portion, a plurality of outward transition portions, and an inward transition portion. The outer layer portion includes a first outer layer portion which is connected to one of the outward transition portions extending from an intermediate position of the inner layer portion and connected to the inward transition portion. The inward transition portion extends to an intermediate position of the inner layer portion.