A liquid crystal display device has a liquid crystal panel and a backlight unit, wherein the backlight unit comprises: a light guide plate, having a bottom surface, a light exiting surface opposite to the bottom surface, at least one lateral light incident surface and at least a lateral side, wherein the lateral side includes a retaining surface; a frame body for receiving the light guide plate, having a stopping part disposed at a position corresponding to the retaining surface, wherein the stopping part is closely engaged with the retaining surface of the light guide plate for fixing the light guide plate; and a light source disposed in the frame body, emitting light toward to the lateral light incident surface.