A prism sheet includes a sheet body that includes opposite light exiting and incident surfaces, and a lateral side transversely connected between the light incident and exiting surfaces. The light exiting surface includes two side regions disposed on two opposite sides of a reference line on the light exiting surface, which is perpendicular to the lateral side. The sheet body further includes a plurality of parallel microstructure members protruding from the light exiting surface and extending perpendicularly to the lateral side. The microstructure members have a distribution density decreased in a density-decreasing direction parallel to the lateral side and pointing toward either of the side regions from the reference line.