A now superconducting material comprising a compound oxide represented by the general formula:(Sr,.gamma.).sub.x (La,.delta.).sub.1-x .epsilon..sub.y Cu.sub.1-y O.sub.3-zin which".gamma." represents an element of IIa group of the periodic table except Sr, an atomic ratio of .gamma. to Sr being selected in a range between 1% and 90%,".delta." represents an element of IIIa group of the periodic except La, an atomic ratio of .delta. to La is selected in a range between 1% and 90%,".epsilon." represents a metal element of Vb group of the periodic table, x, y and z are numbers each satisfies ranges of 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, and 0.ltoreq.z