PURPOSE: To enable the highly reliable jointing of superconducting wires comprising Nb3Sn and the like by using an oxide superconducting material at the joint part of the wires.

CONSTITUTION: Conventional superconducting wires (Nb3Sn) 3 are opposed to each other in an abutted or slantly cutout state. Then, an oxide superconducting material 5 re-crushed after temporary baking is solidified on the joint part of the wires 3 via a sleeve 6 and the like. Thereafter, the superconducting material 5 is locally heated with a carbon electrode 7 fitted or baked in an overall furnace 8 and annealed. According to the aforesaid process, element wires 3 and 3 in the superconducting wires 3 are directly jointed to each other via the oxide superconducting material 5 and, therefore, highly reliable jointing is available without breaking a superconducting state. Also, as the baking temperature of the oxide superconducting material 5 is approximately equal to the diffusion heat treatment temperature of an Nb3Sn wire material, jointing and diffusion heat treatment can be carried out as a common process.