PURPOSE: To improve heat resistance, oil resistance, water resistance, and insulating characteristic by using a polymethyl pentene TPX tape as an inner layer, and winding a polyphenylene sulfide PPS tape on its outer circumference.

CONSTITUTION: A TPX tape 2 having a low dielectric constant is directly wound on a conductor 1 to improve insulating characteristic. However, since the TPX tape is swollen when dipped in an insulating oil, a PPS tape 3 excellent in oil resistance is wound on the circumference, in order to suppress the swelling, to form an insulating layer, whereby an insulating wire 4 is formed. Each number of turns of the TPX tape 2 and the PPS tape 3 is optionally determined, taking the dielectric constant and oil resistance into consideration. For example, when the number of turns of the TPX tape 2 is increased, the dielectric constant of the insulating layer is lowered, and when the number of turns of the PPS tape 3 is increased, the oil resistance is improved.