A laser processing device comprises a laser light source emitting the laser light, a spatial light modulator modulating the laser light emitted from the laser light source, and a converging optical system converging the laser light modulated by the spatial light modulator at the object. A plurality of rows of modified regions include at least an entrance-surface-side modified region located on the laser light entrance surface side, an opposite-surface-side modified region located on the opposite surface side of the laser light entrance surface, and a middle modified region located between the entrance-surface-side modified region and opposite-surface-side modified region. When forming the middle modified region, the spatial light modulator displays an axicon lens pattern as a modulation pattern so as to form converging points at a plurality of positions juxtaposed close to each other along a laser light irradiation direction. When forming the entrance-surface-side modified region and opposite-surface-side modified region, the spatial light modulator is restrained from displaying the axicon lens pattern as the modulation pattern.