MANUFACTURING METHOD OF SUBSTRATE

In the state in which a laser beam is split in such a manner that multiple focal points that line up along a first direction parallel to a specific crystal plane of a single-crystal material that configures an ingot are formed, the ingot and the multiple focal points are relatively moved along a second direction parallel to this specific crystal plane to form a separation layer. In this case, modified parts are formed with each of the multiple focal points being the center of the modified part. In addition, it becomes easier for cracks to extend from these modified parts along the specific crystal plane. Thus, in this case, the cracks formed inside the ingot can be made longer without setting the output power of the laser beam higher. As a result, it becomes possible to improve the throughput in manufacturing a substrate from the ingot.