A method of manufacturing a substrate includes: irradiating, along a first path, a laser beam emitted from a source onto a substrate, wherein the substrate includes a target layer of the laser beam, and wherein the substrate is disposed on a stage; and irradiating, along a second path, a portion the laser beam, which was emitted from the source and reached the target layer, by reflecting the laser beam back onto the target layer using a reflection mirror. An area of a second region of the target layer is greater than an area of a first region of the target layer, wherein the laser beam is irradiated along the second path in the second region, and the laser beam is irradiated along the first path in the first region.