Ion injection is performed to a single crystal silicon wafer to form an ion injection layer, with the ion injection surface of the single crystal silicon wafer and/or the surface of the transparent insulation substrate are/is processed using plasma and/or ozone. The ion injection surface of the single crystal silicon wafer and the surface of the transparent insulation substrate are bonded to each other by bringing them into close contact with each other at room temperature. A silicon on insulator (SOI) wafer is obtained by mechanically peeling the single crystal silicon wafer by giving an impact to the ion injection layer, to form an SOI layer on the transparent insulation substrate, and thermal processing for flattening the SOI layer surface is performed to the SOI wafer, under an atmosphere of an inert gas, a hydrogen gas, and a mixture gas of them.