A panel assembly includes a panel (13), a light-reflecting member (30) and a light-shielding board (50). The panel includes a light-pervious area. The light-reflecting member is coupled to the light-pervious area of the panel. The light-reflecting member forms a light-guiding wall (363) with a plurality of spaced slots (361) therein. The light-shielding board is positioned between the light-guiding wall and the light-pervious area. The light-shielding board defines a plurality of spaced slots (513) corresponding to the slots of the light-guiding wall, light-shielding bars (517) are formed between adjacent slots respectively. The light-shielding board is slidable to cause the slots of the light-shielding board to be removed from the corresponding slots of the light-reflecting member and the light-shielding bars of the light-shielding board to cover the corresponding slots of the light-reflecting member, to thereby shield the light reflected from the light-reflecting member from passing through the light-pervious area.