Provided are a brightness enhancement film including a λ/4 plate, and a reflection polarizer, in which the reflection polarizer includes at least two light reflection layers formed by immobilizing a cholesteric liquid crystalline phase, one light reflection layer of the reflection layers is a layer formed of a polymerizable liquid crystal composition containing a rod-like liquid crystal compound, and the other light reflection layer is a layer formed of a polymerizable liquid crystal composition containing a disk-like liquid crystal compound, and an optical sheet member including the brightness enhancement film, and a liquid crystal display device including the optical sheet member. The brightness enhancement film of the present invention has high brightness and is able to suppress an oblique change in the shade at the time of being incorporated in a liquid crystal display device.