A flat display displays images on both sides is disclosed. The flat display includes a liquid crystal molecule layer disposed between two substrates, and a driving array having a plurality of switch devices disposed on one of the substrates. Images are asynchronously displayed on both sides of the flat display by controlling a rotation state of the liquid crystal molecule layer by the driving array in cooperation with a light source provided by a light source module. The light source module includes two light-guiding plates. One of the light-guiding plates is disposed on the substrate having the driving array, and the other light-guiding plate is disposed on the other substrate having a color filter.