An embodiment of the invention provides a laser annealing method, including the steps of radiating a laser beam to an amorphous film on a substrate while scanning the laser beam for the amorphous film, crystallizing the amorphous film, detecting a light quantity of laser beam reflected from the substrate and a scanning speed of the laser beam while the radiation and the scanning of the laser beam are carried out for the amorphous film, and controlling a radiation level and the scanning speed of the laser beam based on results of comparison of the light quantity of laser beam reflected from the substrate, and the scanning speed of the laser beam with respective preset references.