An optical sheet includes a base layer, a light-condensing layer and a plurality of light-reflecting portions. The base layer includes a first surface and a second surface. The light-condensing layer includes a plurality of light-condensing portions with a first pitch. The light-condensing portions are formed along a first direction of the second surface. The light-reflecting portions are formed in the first surface to be spaced apart from each other along the -first direction in correspondence with a plurality of grooves, each groove formed between two light-condensing portions. An interval distance between a center of the light-condensing portion and an edge of the light-reflecting portion increases when moving toward the edge of the first surface from a center of the first surface along the first direction. Therefore, the number of the optical sheets used for the display device may be reduced.