PROBLEM TO BE SOLVED: To cut a semiconductor wafer quickly into a large number of chips by a method wherein a laser beam is made to irradiate scribe lines to form cutting holes successively scanning the semiconductor wafer in the directions of X and Y at a prescribed pitch so as to separate chips into discrete pieces. SOLUTION: Cut pitches in the directions of X and Y corresponding to the dimensions of a chip are inputted, and the coordinates of non-processing scribe line regions 21a and 22a are designated. A scan control means enables a laser beam to scan a semiconductor wafer at a designated pitch in the direction of X and to scan a semiconductor wafer at a designated pitch in the direction of Y, whereby non-designated scribe lines 21b and 22b except the non-processing scribe line regions are irradiated with a laser beam to form cutting holes to separate chips into discrete pieces. By this setup, the coordinates of regions can be designated in a less time, and a semiconductor wafer can be quickly cut into a large number of chips.