An exemplary prism sheet includes a transparent main body. The transparent main body includes a first surface and a second surface. The first surface and the second surface are on opposite sides of the transparent main body. The first surface defines a plurality of micro-depressions. Each micro-depression forms four inner sidewalls connected with each other. A transverse width of each inner sidewall progressively decreases with increasing distance from the first surface. The second surface defines a plurality of parallelogram microstructures. Each parallelogram microstructure defines four adjacent triangular pyramid depressions.