A laser irradiation apparatus includes a light source that generates a laser beam, a projection lens that radiates the laser beam onto a predetermined region of an amorphous silicon thin film deposited on each of a plurality of thin film transistors on a glass substrate, and a projection mask pattern provided on the projection lens and has a plurality of openings so that the laser beam is radiated onto each of the plurality of thin film transistors, wherein the projection lens radiates the laser beam onto the plurality of thin film transistors on the glass substrate, which moves in a predetermined direction, through the projection mask pattern, and the projection mask pattern is provided such that the openings are not continuous in one column orthogonal to the moving direction.