An exemplary prism sheet includes a transparent main body. The transparent main body has a surface. A plurality of first elongated micro-protrusions and second elongated micro-protrusions protrude from the surface of the main body. Each of the first elongated micro-protrusions extends along a first direction. Widths and heights of each of the first elongated micro-protrusions vary along the first direction. Each of the second elongated micro-protrusions extends along a second direction that intersects with the first direction. Widths and heights of each of the second elongated micro-protrusions vary along the second direction. A method for making the prism sheet and a liquid crystal display device using the prism sheet are also provided.