This laser processing apparatus is for forming modified regions in an object, which includes a sapphire substrate having a C-plane as a main surface, along cutting lines by focusing laser light on the object, and is provided with a laser light source, a spatial light modulator, and a focusing optical system. The spatial light modulator performs aberration correction by a first aberration correction amount smaller than an ideal aberration correction amount when the modified region is formed along a first cutting line along an a-axis direction of the sapphire substrate, and performs aberration correction by a second aberration correction amount smaller than the ideal aberration correction amount and different from the first aberration correction amount when the modified region is formed along a second cutting line along an m-axis direction of the sapphire substrate.