PURPOSE: To obtain a superconductor having high critical temp. and high critical current density and being capable of maintaining superconductivity stably at high temp. by substituting a part of Ba or Sr of a (Y,La)-(Ba,Sr)-Cu-O type superconductor by specified rare earth elements.

CONSTITUTION: A superconductor of this invention has a compsn. described hereunder. A part of Ba or Sr of a (Y,La)-(Ba,Sr)-Cu-O type superconductor is substituted by a rare earth element having an ionic radius approximately equal to that of Ba or Sr, and a part or whole of the rare earth element has tervalency, and residual part bas divalency. Preferred rare earth element is Eu, Sm, or Yb.