An optical mask including a transmissive base substrate, a reflective pattern layer, and a photothermal conversion pattern layer. The reflective pattern layer is disposed on the transmissive base substrate. The reflective pattern layer includes reflectors. The photothermal conversion pattern layer is disposed on the transmissive base substrate among the reflectors. The photothermal conversion pattern layer includes first regions with a first light absorptivity and second regions with a second light absorptivity. The second light absorptivity is greater than the first light absorptivity. The first regions are disposed among the second regions.