PURPOSE: To restrain generation of a birdcage by selecting each hardness of element wires constituting layers of a multiple layer twisted wire conductor in such a manner as to be gradually reduced from the innermost layer toward the outermost layer.

CONSTITUTION: An element wire group W1 which is drawn out of a twisted wire cage Y1 is twisted by a die D1, to pass a compression molding device L1, thus forming a first compressed conductor layer C1. An element wire group W2 which is drawn out of a twisted wire cage Y2 is twisted on the layer C1, thereby forming a second compressed conductor layer C2. An element wire group W3 is twisted on the layer C2, thus forming a third compressed conductor layer C3, and the multiple layer twisted wire conductor thus obtained is wound by a winding machine M. For example, a hard copper wire is used as the element wire of the group W1 constituting the innermost layer C1; a soft copper wire, as the element wire of the outermost layer C3; and a copper wire having intermediate hardness between that of the hard copper wire and that of the soft copper wire, as the element wire of the intermediate layer C2. Accordingly, hardness is reduced gradually from the inner layer toward the outer layer.