A backlight module includes a light source module and a diffuser plate. The diffuser plate has a plate body, a plurality of light-scattering areas and a plurality of light-gathering areas. The light-scattering areas and the light-gathering areas are alternately disposed on a light-entrance surface or a light-exit surface of the plate body. The light-scattering area includes a plurality of cambered units while each cambered unit has a convex cambered surface. The light-gathering area includes a plurality of prism lenses. Two side surfaces of the prism lenses intersect at an angle θ.