PURPOSE: To reduce the m.p. of an oxide, to inhibit a reaction with the material of a crucible at a low temp. and to produce a superconductor at a low cost by carrying out melting in an atmosphere under a low partial pressure of oxygen when a Y-contg. oxide superconductor is produced by melting.

CONSTITUTION: Powdery starting materials such as Y2O3 powder, BaCO3 powder and CuO powder are charged into a platinum crucible and melted by heating at 1,300°C in vacuum or in an atmosphere under a very low partial pressure of oxygen, e.g. an atmosphere of an inert gas such as N2, He or Ar. The resulting melt is rapidly cooled to room temp., pulverized in a mortar and press-molded. This molded body is crystallized by rapid heating to 1,000°C in an atmosphere of gaseous N2 and slow cooling to 900°C and it is further cooled to room temp. in an atmosphere under a high partial pressure of oxygen to produce a Y-contg. oxide superconductor having a compsn. represented hy a formula YBa2Cu3O7-y. Since melting is carried out under the low partial pressure of oxygen, the oxide superconductor is produced at a low cost while preventing a reaction with the material of the crucible at a low temp.