PURPOSE: To prevent reduction in characteristics of superconductor and to improve critical current density, by bringing a specific oxide superconductor through a CuO or Cu2O layer into contact with a substrate and heating.

CONSTITUTION: Oxides, carbonates, etc. of constituent elements of Bi, Sr, Ca and Cu or Tl, Ba, Ca and Cu are blended in an atomic ratio of 2:2:1:2 or 2:2:2:3, calcined in an oxygen atmosphere at 800°C-the melting point, ground, calcined and ground to give oxide superconductor powder 1a and 1b. Then the powder 1a and 1b or an oxide having a lower Cu content than the oxide superconductor is brought into contact through a CuO or Cu2O layer 2a or 2b with a substrate 3a or 3b, heat-treated at 800-900°C and sintered.