A laser device includes a light source part; an optical path adjustment part; a light distribution part that splits a laser beam into a plurality of sub-beams to a substrate; a drive part that moves the light distribution part and adjusts relative positions between the light distribution part and the substrate; a sensing part; and a control part. The control part generates an image based on a signal sensed by the sensing part and measures an image contrast of the image. The control part records and compares a plurality of image contrasts according to the position of the light distribution part to determine an optimal position of the light distribution part.