A method for manufacturing an SOI substrate, including the steps of implanting hydrogen ions from a main surface of a single-crystal silicon substrate having an interstitial oxygen concentration which is equal to or below 1.times.10.sup.18 cm.sup.-3; performing an activation treatment with respect to the main surface of at least one of a transparent insulative substrate and the silicon substrate; bonding the main surface of the transparent insulative substrate to the main surface of the silicon substrate at a room temperature; performing a heat treatment with respect to the bonded substrate at a temperature falling within the range of 350.degree. C. to 550.degree. C. and having a cooling rate after the heat treatment that is equal to or below 5.degree. C./minute; and mechanically delaminating a silicon thin film from the silicon substrate to form a silicon film on the main surface of the transparent insulative substrate.