Transmittable lighting device

A transmittable lighting device is provided to overcome the problem where the lighting quality and transmittance of the conventional smart glass are difficult to balance. The transmittable lighting device includes two substrates electrically connected to a voltage supply and forming a switchable electric field therebetween, a transparent layer between the two substrates, two polarization boards respectively located at two outward sides of the two substrates, and a light source provide an adjustable light enter the side of the transparent layer. The substrate has an aligning direction orthogonal to that of the other substrate. The transparent layer includes a plurality of liquid crystal molecules. Each polarization board has a polarization direction parallel to the aligning direction of the same side substrate. A background light polarized rotates and passthroughs the two polarization boards. When the electric field formed between the two substrates, the adjustable light is scattered and passthroughs the subst