PURPOSE: To obtain a wire with high critical temperature and large critical current density and sintered delicately and firmly by mixing the specific oxide powder and a solution made of organic copper compound, drying and molding the mixture, then baking it at the specific temperature in the oxygen containing gas atmosphere.

CONSTITUTION: The oxide fine powder constituted of rare earth element, alkaline earth metal, copper and oxygen and a solution made of organic copper compound are uniformly mixed and dried to form a viscous liquid, which is molded into a wire, then it is baked at the temperature range of 750W940°C in the oxygen containing gas atmosphere. In this case, the oxide fine powder is temporarily baked at the temperature of 550°C or above, and the average grain size is made 1μm or below, preferably 0.3μm or below in particular. The wire thus obtained is sintered very delicately and finely using copper oxide as sintering auxiliary, end it has stable and high critical current density and high critical temperature for a long time.