To provide an optical sheet having high accuracy of the pitch of unit lenses and facilitating quality control, and to provide a display device having the optical sheet, and a method for manufacturing the optical sheet.

A lenticular lens sheet 12 includes an optical shape part 121A on one surface, the optical shape comprising a plurality of convex unit lenses 122 arranged at least in one direction along the sheet plane; and the optical shape part 121A includes marks M, which are disposed near both ends in the arrangement direction of the unit lenses 122 and each disposed in a convex shape in a valley part between the unit lenses 122, and which are to be used for measuring a length in the arrangement direction of the unit lenses 122. The mark M is disposed at least one in each of the areas close to both ends in the arrangement direction of the unit lenses 122 of the optical shape part 121A, with the apex of the mark lower than the apex of the unit lens 122.