A reflection sheet and backlight unit including the same are disclosed. In one aspect, the reflection sheet includes a bottom surface, a plurality of side surfaces, each extending from the bottom surface and having an edge opposing the bottom surface, and a first cutting line formed in at least a first one of the side surfaces from a boundary between the first side surface and the bottom surface toward the opposing edge of the first side surface. The reflection sheet also includes a cover surface extending from the opposing edge of the first side surface, wherein the cover surface comprises a protruding surface protruding toward the first cutting line.