A laser crystallization device includes a laser oscillator, a stage, and a reflection unit. The stage is configured to support a substrate with a target film disposed on the substrate. The laser oscillator is configured to irradiate an incident laser beam on the target film. The stage is configured to move the substrate such that the incident laser beam scans the target film. The incident laser beam is reflected from the target film to generate a reflected laser beam. The reflection unit includes at least two reflection mirrors positioned at a path of the reflected laser beam. The reflection unit is configured to re-irradiate the reflected laser beam on the target film two or more times through a plurality of paths that are different from a path of the incident laser beam.