A laser device may include a light source configured to emit a laser beam in burst operation, an optical sensor configured to acquire a cross sectional image of the laser beam during a certain period for every certain cycle, an image processor configured to receive an input of an image signal of the cross sectional image outputted from the optical sensor and output beam relating information about the laser beam, a beam traveling direction adjuster configured to adjust a traveling direction of the laser beam, and a controller configured to control the beam traveling direction adjuster based on the beam relating information when at least a part of a period in which the optical sensor acquires the cross sectional image is overlapped with a period in which the light source emits a laser beam.