PURPOSE: To obtain the high-density oxide superconducting material having a high critical current density by forming the raw powder for an oxide superconductor having a monolayer and sintering the formed body while specifying the temp., compressive stress and oxygen content in the atmosphere.

CONSTITUTION: The raw powder for an oxide superconductor (shown by the formula) having a monolayer is compacted into a bulk or a sheet, or the raw powder is packed into a sheath and then applied with a cold working such as drawing. Uniaxial compressive stress at 50kg/cm2 is exerted on the formed material at a temp. ranging from directly below the m.p. of the superconducting monolayer to 30°C, and the formed material is sintered in the atmosphere contg. ≤20% oxygen. When the sintered material is cooled, the uniaxial compressive stress is reduced to obtain a final sintered body having ≥99% compactness of the theoretical density. An oxide superconducting material having a high critical current density is obtained in this way.