Since the principal surface of a silicon substrate (12) is (100) surface, a crack (17) generated starting from a melt treatment region (13) extends in the cleavage direction of the silicon substrate (12) (direction orthogonal to the principal surface of the silicon substrate (12)). In this case, since the back surface (1b) of an object (1A) to be processed and the front surface (10a) of an object (10A) to be processed for separation are bonded by anodic bonding, the crack (17) reaches the front surface (1a) of the object (1A) to be processed in a continuous fashion and without almost changing the direction thereof. In addition, when a stress is generated in the object (10A) to be processed for separation, since the crack (17) reaches the back surface (10b) of the object (10A) to be processed for separation, the crack (17) easily extends on the side of the object (1A) to be processed.