PURPOSE: To produce the titled ceramic powder having a high oxygen content, superior superconductive characteristics and high density by melting superconductive ceramic powder, rapidly cooling the resulting melt under pressure to form a thick crystal film and subjecting the film to heat treatment, oxidation and grinding.

CONSTITUTION: Superconductive ceramic powder 1 is put in a platinum nozzle 2 and melted by heating at the m.p. or above (1,250W1,450°C) for 1W5min. Gas 3 is jetted into the nozzle 2 from the top to spout a gob of the resulting melt 1 out of the bottom hole 4 in the nozzle 2 and the gob is rapidly cooled under pressure with a twin-roll type very rapid cooling device 5 to obtain a thick crystal film of 10W80mm length, 5W15mm width and 5W300μm thickness. This film is heat treated at 850W950°C for 2W60hr in an atmosphere contg. oxygen or in oxygen plasma to form a perovskite phase. A superconductive phase is then formed by oxidation at 200W700°C for 5W24hr in the same atmosphere and the film is ground.