When manufacturing a bonded substrate using an insulator substrate as a handle wafer, there is provided a method for manufacturing a bonded substrate which can be readily removed after carried and after mounted by roughening a back surface of the bonded substrate (corresponding to a back surface of the insulator substrate) and additionally whose front surface can be easily identified like a process of a silicon semiconductor wafer in case of the bonded substrate using a transparent insulator substrate as a handle wafer. There is provided a method for manufacturing a bonded substrate in which an insulator substrate is used as a handle wafer and a donor wafer is bonded to a front surface of the insulator substrate, the method comprises at least that a sandblast treatment is performed with respect to a back surface of the insulator substrate.