PURPOSE: To improve cooling and insulating properties of a winding by winding a surface of superconductive wire with a tape made by providing a nonwoven fabric with longitudinal and lateral grooves and by heating said fabric to bring it to self-fusion-weld.

CONSTITUTION: An insulating tape 3 with longitudinal and lateral grooves 2 composed of a nonwoven fabric 1 of polyester fiber is wound on to a superconducting wire 4 and then the obtained product is wound round a drum. After that, power is applied to said drum to heat the superconducting wire 4 to about 180°C to cause self-fusion-weld of the fiber of said nonwoven fabric 1 to a surface of the superconducting wire 4 and form an insulated superconducting wire 5. Thus, a self-fusion-weld face 6 of said fiber adheres strongly to enable preventing the insulating tape 3 from easily peeling off from the superconducting wire 4.