PURPOSE: To make it possible to reduce the production of cracks in the epoxy resin layer by a method wherein a resin-impregnated tape is wound around a super-conductive wire, the inter-wire gap is filled with resin-impregnated reinforcing material, and filler having favorable heat-conductivity is mixed into the impregnated epoxy resin.

CONSTITUTION: A resin-impregnated tape such as glass cloth tape 26 is wound around a super-conductive wire 22a, and the inter-wire gap where the super- conductive wire 22a is wound is filled with resin-impregnated reinforcing material 27 where filler having favorable heat-conductivity is mixed into the impregnating epoxy resin 28. With this method, the glass cloth tape 26 is wound around the surface of the super-conductive wire 22a, and the inter-wire gap 23 where the super-conductive wire 22a is wound is filled with resin-impregnated reinforcing material 27, and the filler with favorable heat conductivity is mixed into the impregnating epoxy resin 28, providing the super conductive field winding capable of reducing the production of cracks in the epoxy resin layer 25a.