A joining product of oxide superconducting materials having a high current density and process for producing the same. A joining product comprising a plurality of oxide superconducting materials having an identical crystal orientation joined with each other through a superconducting phase of the same type as described above which has the same crystal orientation as the oxide superconducting materials and a lower peritectic temperature than the oxide superconducting materials. A joining method comprising the steps of: regulating oxide superconducting materials to be joined so that they have an identical crystal orientation; either inserting as a solder a material comprising elements constituting an oxide superconductor having a lower peritectic temperature than the oxide superconducting materials or bringing the material comprising elements constituting an oxide superconductor having a lower peritectic temperature than the oxide superconducting materials into contact with the oxide superconducting materials to be joined; heating the assembly to a temperature below the peritectic temperature of the superconducting materials to be joined and above the peritectic temperature of the solder; and gradually cooling the heated assembly to orient and grow the same type of oxide superconductor at the joining interface. A junction product of oxide superconducting materials free from such crystal grain boundary as to inhibit the current flow and having a high critical current density can be provided and can be utilized as a magnet, a magnetic shield and a current leading material.