A laser crystallization apparatus includes a laser generator that generates a laser beam including a plurality of line beams that are parallel to each other. An optical system includes a plurality of lenses and mirrors, wherein the optical system optically converts the generated laser beam to a converted laser beam. A chamber includes a stage and a substrate disposed on the stage, wherein a laser-crystallized thin film is formed on the substrate when the substrate is irradiated by the converted laser beam. A line focus adjuster that adjusts a line focus and a final focus of the plurality of line beams passing through the optical system, wherein the substrate is irradiated by the plurality of line beams at the final focus of the plurality of line beams.