The present invention relates to a prism sheet having a side which is perpendicular to the normal of a light guiding plate. The prism sheet includes a prism sheet base film and a plurality of linearly aligned prisms. The prisms are formed on one side of the prism sheet base film. Here, one side of each prism is perpendicular to the prism sheet base film. The prism sheet condenses a light outputted from a light guiding plate using its internal total reflection, and so the efficiency of the light is enhanced.