PURPOSE: To prevent the intrusion of impurities into a precursor by using a casting mold with the inner wall surface made of copper and casting the precursor in the mold heated above the glass transition temp. of the superconductor.

CONSTITUTION: The casting mold 1 to be used consists of the two cylinders having different diameters and is made of copper. A cylindrical Bi-based oxide superconductor precursor is cast in the mold. In this case, the mold 1 is firstly heated to about 500°C, and molten Bi2Sr2CaCu2Ox 3 is poured into the cavity 2 from the gate. The melt 3 is obtained by sufficiently mixing 2 kg of the Bi2O3, SrCO3, CaCO3 and CuO in total (Bi:Sr:Ca:Cu=2:2:1:2) in a mortar and heating the mixture in a platinum crucible 4 to 1100°C to melt the mixture. The mold 1 contg. the melt 3 is cooled to room temp. at the rate of 50°C/h, and then the cast body 5 is discharged.