When a thermal expansion coefficient of a handle substrate is higher than that of a donor substrate, delamination is provided without causing a crack in the substrates. A method for producing a bonded wafer, with at least the steps of: implanting ions into a donor substrate (3) from a surface thereof to form an ion-implanted interface (5); bonding a handle substrate (7) with a thermal expansion coefficient higher than that of the donor substrate (3) onto the ion-implanted surface of the donor substrate to provide bonded substrates, subjecting the bonded substrates to a heat treatment to provide an assembly (1), and delaminating the donor substrate (3) of the assembly (1) at the ion-implanted interface wherein the assembly (1) has been cooled to a temperature not greater than room temperature by a cooling apparatus (20), so that a donor film is transferred onto the handle substrate (7).