Fractures (17a, 17b) are generated from modified regions (7a, 7b) to front and rear faces (12a, 12b) of a object to be processed (1), respectively, while an unmodified region (2) is interposed between the modified regions (7a, 7b). This can prevent fractures from continuously advancing in the thickness direction of a silicon substrate (12) when forming a plurality of rows of modified regions (7). By generating a stress in the object (1), the fractures (17a, 17b) are connected to each other in the unmodified region (2), so as to cut the object (1). This can prevent fractures from meandering in the rear face (12b) of the object (1) and so forth, whereby the object (1) can be cut accurately along a line to cut the object (5).