A semiconductor package including a prism sheet having dam structure disclosed. The semiconductor package includes a case having a wall configured for surrounding a space in which a semiconductor chip is installed, and a prism sheet having a prism surface consisting of a plurality of prism peaks and a plurality of prism valleys and a flat surface facing the prism surface, wherein the prism surface faces the semiconductor chip and the flat surface is coupled to a cover, wherein a dam extending in a direction different from an extending direction of the prism peak is formed on the prism surface.