Crystal quality improving method of a bonded substrate subjected to sandblasting

Provided is a method to prevent micro defects from being generated, in a process in which a peeling-off damaged layer of a Si-layer is to be removed by etching, and a donor film is to be formed, when implementing sandblast processing on the handle-substrate side, after forming the Si-layer with the SiGen method or the like, and after protecting the surface of a paste-together layer in advance. Provided is a method of manufacturing a paste-together substrate equipped with a donor film on the handle-substrate, which comprises: a process (S1) in which the paste-together layer is formed on aforementioned handle-substrate, with the ion-implantation peeling-off method; a process (S2) in which the surface of aforementioned paste-together layer is covered with a protection member; a process (S3) in which sandblast processing is implemented on the surface of aforementioned handle-substrate; a process (S5) in which aforementioned protection member is peeled off; a process (S6) in which washing without any etching effect is implemented on the surface of the paste-together layer that already had aforementioned peeling-off of protection member implemented; and a process (S7) in which aforementioned donor film is formed, by performing chemical etching on the surface of the paste-together layer that already had aforementioned washing process implemented.