To provide an optical sheet capable of improving front brightness and capable of functional unification with a separate optical sheet.

The optical sheet, in which a plurality of transparent protrusions are arranged with an interval on at least one surface of a transparent substrate and top end parts of the transparent protrusions have substantially parallel flat planes with respect to the transparent substrate surface, is characterized in that a part of light rays, emitted from groove parts existing between the transparent protrusions, is refracted and proceeds to neighboring transparent protrusions, is totally reflected on the upper surface of the transparent protrusions and is recovered, thereby, the loss of light rays is reduced and the front luminance is improved. In addition, the optical sheet is capable of function unification by laminating another optical sheet, because the upper surface of the transparent protrusion is flat.