The present invention provides an LCD device, which includes a lower substrate (10) and an upper substrate (20) opposite to each other, a liquid crystal layer (30) interposed between the lower substrate (10) and the upper substrate (20), and a side-edge backlight source (40) disposed at one lateral side of the lower substrate (10). The lower substrate (10) includes a first backing base plate (11) and a first polarization layer (13) disposed on one side of the first backing base plate (11) that is adjacent to the liquid crystal layer (30). The upper substrate (20) is a TFT array substrate. By making use of the advantages of the lower substrate of being simple in respect of the manufacturing process and the structure over those of the TFT array substrate, the arrangement of the first polarization layer provided on the lower substrate could be made an internally built structure with the first backing base plate of the lower substrate serving as a light guide plate for the side-edge backlight source so that there is no need to further include an additional light guide plate and thus making the LCD device feature an ultrathin modular structure with optimized displaying performance.