Disclosed is a method for reprocessing a semiconductor substrate which is by-produced in manufacturing a silicon-on-insulator substrate. The method includes: forming an embrittlement layer in a single crystal semiconductor substrate; bonding the single crystal semiconductor substrate with a base substrate having an insulating surface; and separating the single crystal semiconductor substrate along the embrittlement layer to give a silicon-on-insulator substrate and a semiconductor substrate to be reprocessed. The above steps provide, in the peripheral portion on the semiconductor substrate, a projection comprising the embrittlement layer and a single crystal semiconductor layer over the embrittlement layer. The method is characterized by an etching step to selectively remove the projection without etching a portion where the projection is absent, which allows the semiconductor substrate to be reused for the production of another silicon-on-insulator substrate.