Abstract: A method of manufacturing a display device includes providing a mother substrate including a first cell region, a second cell region, and a peripheral region. First alignment keys arranged in a first direction in the peripheral region on the mother substrate is formed such that the first alignment keys are adjacent to a first side portion of each of first and second light emitting structures, while forming the first and second light emitting structures in the first and second cell regions on the mother substrate, respectively. A photoresist is formed in a second direction on the first and second light emitting structures by using a coater such that the photoresist does not to overlap the first alignment keys. The mother substrate is rotated at a preset angle. A light is irradiated to the photoresist by moving an exposer in a direction in which the first alignment keys are arranged.