The invention discloses a side-in backlight module, which comprises a plurality of light control units which can be independently controlled, wherein the light control unit comprises a first substrate, a first electrode, a polymer liquid crystal layer, a second electrode and second substrates which are sequentially disposed, a side surface of the polymer liquid crystal layer is provided with a light shielding layer, and the first electrode and the second electrode are used to form an electric field applied on the polymer liquid crystal layer to adjust scattering state of light by the polymer liquid crystal layer, wherein at least the second electrode and the second substrate are transparent, and the second substrates of all the light control units are sequentially closely joined to form alight guide plate, and a side surface of the light guide plate is provided with a light source. The invention also discloses a liquid crystal display device comprising the side-in backlight module. The side-in backlight module can realize the partial dimming by using the side-in backlight to realize the partition block control, and realize the effect of high dynamic contrast, and is also beneficial to the thin and light development of the liquid crystal display device.