A method for producing hybrid substrates which can be incorporated into a semiconductor production line involves: forming an ion-injection region (3) by injecting ions from the surface of a silicon substrate (1); adhering the ion-injection surface of the silicon substrate and the surface of a sapphire substrate (4) to one another directly or with an insulating film (2) interposed therebetween; and then obtaining a hybrid substrate (8) having a silicon thin-film (semiconductor layer; 6) on the sapphire substrate (4), by detaching the silicon substrate (1) in the ion-injection region (3). This method is characterized in that the adhering to the silicon substrate (1) occurs after the sapphire substrate (4) is heat-treated in advance in a reducing atmosphere.