Laser processing device and laser processing method

A laser processing device comprising:

• a laser irradiation unit that irradiates an object including a first surface and a second surface opposite to the first surface with a laser beam using the first surface of the object as an incident surface;
• and
• a control unit, including at least one processor, that:
• performs a first control to control the laser irradiation unit to form first modified regions for division and cracks extending from the first modified regions in a direction of the second surface inside the object by performing irradiation with the laser beam while moving a condensing spot of the laser beam relative to the object along each of a plurality of first lines extending in a first direction along the incident surface,
• performs a second control to control the laser irradiation unit to form second modified regions for division and cracks extending from the second modified regions in the direction of the second surface inside the object by performing irradiation with the laser beam while moving the condensing spot of the laser beam relative to the object along each of a plurality of second lines intersecting the first direction and extending in a second direction along the incident surface, after the first control, and
• performs a third control to control the laser irradiation unit to form a plurality of third modified regions for suppressing warpage and cracks extending from the third modified regions inside the object by performing irradiation with the laser beam before the second control, the cracks being formed to reach the first surface and not to be continuous with the cracks extending from the first modified regions.