Abstract: A backlight module includes a light guide plate which has a first sidewall and two opposite second sidewalls extending transversely of the first sidewalls. The first and second sidewalls interconnect two opposite first and second faces. Alight source is disposed at one of the second sidewalls and projects light rays onto the first sidewall at an oblique angle. A first reflection layer is disposed over the first sidewall, and a second reflection layer is disposed over the second face. Total reflection of light into the light guide plate from the first sidewall and second face increases brightness and enhances evenness of brightness.