To decrease the number of boundaries and to lessen the reflection loss by integrating two prism sheets with one Fresnel plate.

Many regular quadrangles which are constant in line widths and copossess a centroid point are so arranged that the sides of these quadrangles are parallel. The condensing sheet close-packed and arrayed with the unit regular quadrangular Fresnel plates 41 each constituted in such a manner that the change rate of the similitude ratio to the innermost regular quadrangle decreases according to the distance from the centroid point two dimensionally and regularly on a transparent substrate is manufactured by a UV curing method. The respective sides of the quadrangles constituting the regular quadrangular Fresnel plates decrease in the spacings of the adjacent sides from the inner peripheral part toward the outer peripheral part. Then, the diffraction angle s larger nearer the outer peripheral part of the unit regular quadrangular Fresnel plates 41. Namely, the unit regular quadrangular Fresnel plates 41 exhibit the condensing effect similar to the condensing effect of a convex lens and the assembly of the unit regular quadrangular Fresnel plates 41 is the condensing sheet for backlight which efficiently illuminates an LCD panel with the luminous flux having directivity.