The present invention is directed to a method for manufacturing an SOI wafer in which the bonded SOI wafer after the delamination by the ion implantation delamination method is subjected to a rapid thermal oxidation process such that an oxide film is formed on a surface of the SOI layer, the oxide film is removed, the bonded SOI wafer is then subjected to a flattening heat treatment to flatten the surface of the SOI layer, the flattening heat treatment causing migration of silicon atoms of the surface of the SOI layer, and the bonded SOI wafer is then subjected to a sacrificial oxidation process to adjust a film thickness of the SOI layer. The method enables efficient manufacture of a high quality SOI wafer having an SOI layer with sufficiently reduced surface roughness of the SOI layer surface and fewer deep pits in the SOI layer surface.