The present invention provides a method for manufacturing optical sheet having an improved appearance, optical sheet, and an image display device having the optical sheet. The method for manufacturing optical sheet having a plurality of layers in which at least one layer is an optical functional sheet layer comprises: light-transmissive portions configured to be arranged in a row along the surface of a base material layer; and light-absorbing portions arranged between the light-transmissive portions, the method comprising the steps of: forming the light-transmissive portions on one side of the base material layer; and forming the light-absorbing portions repeatedly by filling a binder made of a resin in which light-absorbing particles are dispersed in the gaps between the light-transmissive portions and curing the binder, wherein at least the last step of the repeating step for forming the light-absorbing portions is carried out so that the density of the light-absorbing particles contained in the binder is lower than the density of the same at the first step for forming the light-absorbing portion. The optical sheet is produced by the method; and the image display device is provided with the optical sheet.