PURPOSE: To prevent the reduction of the critical current density by the thermal distortion and the occurrence of cracks generated by thermal distortion at the time of the heat cycle and obtain high current density for a long time by forming a slit on a metal film.

CONSTITUTION: A slit 4 reaching an oxide superconductor 4 is formed along the longitudinal direction on the metal film 1 of the oxide superconducting wire 4. In this case, various kinds of oxide superconductors can be used, but when the perovskite type oxide superconductor containing a rare earth element is used, the practical effect is large in particular. The thermal distortion due to a difference in the thermal expansion coefficient between the metal coating 1 and the oxide superconductor 4 is absorbed by the opening and closing of the slit 2. The reduction of the critical current density due to the thermal distortion and the occurrence of cracks at the time of the heat cycle are prevented, and high current density is obtained for a long time.