An optical film and a display device having the same are provided. The optical film has a light input face, a light output face opposite to the light input face, and a light-output structure disposed on the light output face. The light-output structure includes a plurality of light output microstructures such as prisms disposed side by side along a first direction on the light output face. Each prism has a first quadrilateral cross section parallel to the first direction. A first side of the quadrilateral cross section is connected to the light output face and includes a first angle with the light output face, wherein the first angles of the prisms continuously arranged have angle values varying in a periodic manner.