PURPOSE: To enhance the critical temp. and critical current by using a sheath of cylindrical braid of filament made of Cu or Cu alloy, and by adjusting the treatment environment prior to sintering to oxygen enriched atmosphere upon once vacuum drawing.

CONSTITUTION: Ceramic type superconductive powder is filled while a plurality of extra-thin wires of Cu or Cu alloy to form a sheath is braided, to provide material to wire. This undergoes cold drawing until desired wire dia. is attained. The resultant is put in a heat treatment furnace, and upon once vacuum drawing, it is subjected to sintering and annealing while adjustment is made to a certain O2 concentration. Thus oxygen void generated when the filling powder is sintered, is avoided to lead to enhancement of the critical temp. and critical current.