A laser processing device includes a support unit, a laser light source, a spatial light modulator, and a condensing unit. A modulation pattern displayed on a display unit of the spatial light modulator includes a branching pattern for branching laser light into first branched laser light components to form a first groove and second branched laser light components to form a second groove. A distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light adjacent to each other in a direction along the line is larger than a distance between the position of the focusing point of the first branched laser light and the position of the focusing point of the second branched laser light in the width direction of the first groove and the second groove.