A deposition mask set includes a first mask, a second mask, and a third mask. Each of the first mask, second, and third masks includes a first edge substantially parallel to a first direction, a second edge substantially parallel to a second direction, and a plurality of first openings. Each of the openings includes a first opening side that is substantially parallel to a third direction and a second opening side that is substantially parallel to a fourth direction, and each of the openings corresponds to one of a first, second, or third color area at one of pixel areas. The third and fourth directions are not parallel to the first and second directions, and the first, second, and third color areas are adjacent to each other in the third direction.