Oxide superconductor and method of producing same

An oxide superconductor composed of Cu, O and at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca and consisting of alternately arranged at least one oxygen-deficient perovskite structure section and at least one infinite layer structure section,

• said perovskite structure section consisting of two first atomic layers each consisting of O and an element M.sup.1 which is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca and each having an atomic ratio O/M.sup.1 of 1 or less, wherein M.sup.1 in each of said two first layers is the same, and a second atomic layer sandwiched between said first atomic layers, said second atomic layer consisting of O and Cu and having an atomic ratio O/Cu of 2 or less,
• said infinite layer structure section consisting of j-number and k-number of third and fourth atomic layers, respectively, wherein j is an integer of 1 or more and k is equal to j-1, said third and fourth atomic layers being alternately arranged when is 2 or more,
• each of said j-number third atomic layers consisting of O and Cu and having an atomic ratio O/Cu of 2, and
• each of said k-number fourth atomic layers consisting of an element M.sup.2 which is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, wherein M.sup.2 in each of said fourth atomic layers is the same.