The study of superconductor-applied devices has been and is being made by way of thin film processing on single crystal substrates. In accordance with developments of positive research for more sophisticated devices, the substrates of better quality come to be required among superconductor researchers. This eventually drives the substrate manufacturers to developing ever-new substrates and further improving chemical/physical qualities of conventional substrate. This paper introduces each single crystal substrate being applied to oxide superconductor thin film processings, followed by general remarks of oxide superoconductors and growth methods of single crystals for use as substrates.