To provide an aligner, exposure method, and a method for manufacturing a display device wherein, in relation to an aligner for screen compositing, unevenness in partitions on a sensitized substrate caused by exposure amount is reduced.

A pattern on a reticle 9 is exposed and developed on a sensitized substrate 11 so that parts of a plurality of partitions overlap each other, brightness of a resist image in each region and overlapped regions is detected, and the position of a reticle blind 6 and driving during exposure are controlled (16) according to the difference in brightness for controlling the exposure amount, thus unevenness in partitions is reduced.