A laser crystallization apparatus includes a laser generating module configured to generate a laser beam, an optical module configured to guide the laser beam, an annealing chamber comprising a stage on which a target substrate comprising an amorphous thin film formed therein is disposed, the stage being movable along an X-axis direction and a Y-axis direction, and a tilt refractive lens configured to transform the laser beam having a cross-sectional area of a rectangle shape into a tilted laser beam having a cross-sectional area of a non-rectangular parallelogram shape and to irradiate the tilted laser beam perpendicular to the stage.