An exemplary prism sheet includes a light input surface, a light output surface opposite to the light input surface, and a plurality of triangular pyramidal micro-elements and a plurality of hexagonal pyramidal micro-elements. The triangular pyramidal micro-elements and the hexagonal pyramidal micro-elements are formed on the light output surface. Each triangular pyramidal micro-element surrounded by three adjacent hexagonal pyramidal micro-elements. Bottom surfaces of each hexagonal pyramidal micro-element and each triangular pyramidal micro-element are coplanar with the light output surface. A liquid crystal display device using the prism sheet is also provided.