A light condensing filter has plural prisms formed on a surface of a flat substrate and on the opposite surface to the surface, and light from a light source is condensed by the plural prisms, wherein the plural prisms formed on the surface are designed in a linear shape extending in a specific direction on the surface and arranged in a direction perpendicular to the specific direction, the plural prisms formed on the opposite surface are designed in a linear shape extending in the direction perpendicular to the specific direction on the opposite surface and arranged in the specific direction, and the plural prisms formed on the surface and the plural prisms formed on the opposite surface are irregularly arranged.