The present invention is a method for manufacturing an SOI wafer, including: implanting one or more gas ion selected from a hydrogen ion and a rare gas ion into a bond wafer composed of a semiconductor single crystal substrate from a surface of the bond wafer to form an ion-implanted layer; bonding the surface from which the ion is implanted into the bond wafer and a surface of a base wafer through an oxide film; and then delaminating the bond wafer at the ion-implanted layer by performing a delamination heat treatment with a heat treatment furnace to form the SOI wafer, wherein after the delamination heat treatment, a temperature of the heat treatment furnace is decreased to 250° C. or less at temperature-decreasing rate of less than 3.0° C/min, and then the SOI wafer and the bond wafer after delamination are taken out from the heat treatment furnace.