The present invention provides a liquid crystal display device, which includes a backlight module and a liquid crystal panel disposed on the backlight module. The backlight module includes an optic film assembly. The optic film assembly includes a first prism plate. The liquid crystal panel includes a first polarization plate. The first polarization plate is arranged to directly confront the first prism plate. The first prism plate includes a first base plate and a plurality of parallel first prism bars formed on an upper surface of the first base plate. The first prism bars have an axial direction that forms an included angle with respect to a polarization direction of the first polarization plate. The liquid crystal display device omits the topmost diffusion plate that is conventionally used in the known the optic film assembly so as to reduce the manufacture cost.