A prism sheet capable of achieving an enhancement in light efficiency and viewing angle characteristics and a backlight unit using the prism sheet are disclosed. The prism sheet includes: a condensing film which transmits light incident to the condensing film; a plurality of prism crests on the condensing film having apexes; and a plurality of reflection patterns formed on the condensing film such that each of the reflection patterns faces a boundary of adjacent prism crests associated with the reflection pattern to reflect light incident onto the reflection patterns.