A method of making bonded SOS substrate with a semiconductor film on or above a sapphire substrate by implanting ions from a surface of the semiconductor substrate to form an ion-implanted layer; activating at least a surface of one of the sapphire substrate and the semiconductor substrate from which the ions have been implanted; bonding the surface of the semiconductor substrate and the surface of the sapphire substrate at a temperature of from 50° C. to 350° C.; heating the bonded substrates at a maximum temperature of from 200° C. to 350° C.; and irradiating visible light from a sapphire substrate side or a semiconductor substrate side to the ion-implanted layer of the semiconductor substrate to make the interface of the ion-implanted layer brittle at a temperature of the bonded body higher than the temperature at which the surfaces were bonded, to transfer the semiconductor film to the sapphire substrate.