A laser processing apparatus has one laser light source that simultaneously radiates laser beams with two wavelengths. Depth positions of focusing points for laser beams are gradually changed in a wafer. Three sets of modifying region groups, i.e., six layers of modifying region groups, are successively formed. One set of modifying region groups constitutes two layers and is formed at a time. The modifying region groups are separated, adjoined, or overlapped with each other along an estimated cut line of the wafer in a depth direction from a surface thereof.