In an optical sheet which is used for light control illumination in a backlight unit for a display, in order from an incident side of an illuminating light, there are provided at least a light scattering layer which scatters the illuminating light toward an outgoing surface side, an adhesion layer or an adhesive layer, a light reflection layer which reflects light scattered by the light scattering layer toward the light scattering layer side, and a lens sheet whose flat rear face is fixed to the other side of the light reflection layer, and in which a plurality of unit lenses are disposed on the surface. Opening portions corresponding to the respective unit lenses one-to-one are provided to the light reflection layer, and thickness of the adhesion layer or the adhesive layer is thinner than that of the light reflection layer.