To provide a laser processing method which is capable of enhancing the dividing performance according to a required quality. By irradiating an object to be processed with a laser light L having a pulse waveform in which its half width and its bottom width are equal to one another, a plurality of modified spots are formed along a line to cut inside the object, and a modified region is formed with the plurality of modified spots. Here, a laser light source 101 controls a drive power source 51 by a laser light source controller 102, to switch among a pulse waveform among first to third pulse waveforms according to a PE value of the laser light L. In the case of a low PE value, a first pulse waveform formed such that a peak value is located on its first half side and into a saw-blade shape is set as the pulse waveform, and in the case of a high PE value, a second pulse waveform formed such that a peak value is located on its latter half side and into a saw-blade shape is set as the pulse waveform.