The present invention provides a high-temperature oxide superconductor which comprises an oxide expressed as (Bi 1-x A x ) - By - Cz -Cu oxide (where A is Sb and/or As; B and C are elements different from each other, each being one or more elements selected from Be, Mg, Ca, Sr and Ba; and 0 ≦ x According to the present invention, it is possible to manufacture a high-temperature oxide superconductor having a transition temperature of over 100 K and not containing a rare-earth element at all, and to manufacture a superconductor excellent in reliability and stability more easily than conventional superconductors such as Y-Ba type superconductors.