First, mapping data storing interrupted areas is obtained. In a first modified-layer forming step, before a stacked article is stacked on a front surface of a substrate, a laser beam is directed to the interrupted areas based on the mapping data to form modified layers only at the interrupted areas. After the stacked articles have been stacked on the substrate, in a second modified-layer forming step, the laser beam is directed at least to the predetermined dividing line formed with no modified layer in the first modified-layer forming step to form a modified layer.