According to a conventional production method for an insulated wire having a cross section of any shape other than round, it was hitherto difficult to continuously produce the insulated wire, beginning with feeding of a round wire raw conductor and ending with completing of the insulated wire as a final product. The reason for the difficulty is that the conventional production method needed two or more many steps, each having a different wire speed. The formation of a so-called rectangular wire, in which a conductor takes in the shape of rectangular, is explained, as an example, below. First, a round wire raw conductor is rolled, by means of a rolling mill, plural times, until the conductor becomes a determined size. The rolled conductor is once wound around a bobbin as layer winding. Thereafter, from the bobbin, the rectangular conductor is fed to an enameling machine, for annealing, enameling and winding, or the rectangular conductor is set in an extruder, to be coated with a resin. Thus, the conventional production method needed at least two steps, such as the rolling step, and the enameling or extrusion step. These two steps are considerably different from each other in wire speed capable of being processed in each step. Therefore, it was hitherto difficult to continuously carry out all steps in the conventional production method for insulated wire.
As mentioned above, the conventional production method for insulated wire needed two or more steps, each having a different wire speed. As a result, the following problems arose:    (i) Both the rolling step and the insulation-coating step must be separated, which results in greater cost.    (ii) Plural steps are needed, which results in long lead time.    (iii) The rolling is successively carried out in the thickness direction and in the width direction, so that dimensional precision of the final thickness, width, and corner radius (R) is not high.    (iv) The winding and the feeding, such as the winding after rolling and the feeding to the resin-coating step, are repeated, such that the surface of the conductor is apt to become scratched, which results in deterioration of the surface quality.    (v) The drawing may be conducted by a drawing die after rolling by driven rolls. However, elongation (stretching) in both the longitudinal direction and the width direction is not definite, so that any means, such as a tension-controlling apparatus, is needed, to make addition to a driving system of each roll, which results in a sharp increase in the cost of equipment.