On a first intermediate layer provided on a substrate and having an excellent surface smoothness, are formed a second intermediate layer and an YBCO superconductor layer having excellent properties. An YBCO superconductor (10) having a critical current density (Jc) of 1 MA/cm2 or higher can be produced by forming a first intermediate layer (2), a second intermediate layer (3), an YBCO superconductor layer (4) and an Ag-stabilized layer (5) on the surface of a tape-shaped biaxially oriented Ni—W alloy substrate (1), wherein the first intermediate layer (2) has a thickness of 5 nm or less, has a surface smoothness, comprises A2Zr2O7, and is formed by repeating coating and provisional burning several times by the MOD method, the second intermediate layer (3) comprises a CeO2 film and is formed by the pulse plating method, the YBCO superconductor layer (4) is formed by the MOD method, and the Ag-stabilized layer (5) is formed on the YBCO superconductor layer (4).