The invention provides a prism sheet, back light unit and liquid crystal display device having the same. The prism sheet comprises: a base film; and a plurality of prisms formed on the base film, the prism being extended from one side to another side of the base film and having triangle shaped cross section, wherein the prisms adjacent to each other have different heights, and a height differencebetween the adjacent prisms is approximately 1.2-1.5 [mu]m. The prism sheet prevents the occurrence of a moire pattern and a wet-out phenomenon by increasing irregularity of prisms formed thereon, byconfiguring the prisms adjacent to each other to have different heights, and by differently forming widths of triangular sectional surfaces of one prism according to positions. As the height difference of the prisms adjacent to each other is set as 1.2-1.5 [mu]m, a pressure applied to the prism sheet is distributed to the prisms. This may prevent deformation of the prisms.