An LCD includes a liquid crystal panel having a TFT substrate, a CF substrate, and a liquid crystal layer interposed between the two substrates; a TFT ambient light photosensor having a semiconductor layer for detecting external light; a photodetector unit having a capacitor in which a predetermined reference voltage is charged and a voltage charged by leakage current of the TFT ambient light photosensor is lowered; and an ambient light photosensor reader unit for reading a voltage charged in the capacitor for a predetermined read period. The photodetector unit is disposed on a first surface of the TFT substrate that is in contact with the liquid crystal layer, and the surface of the photodetector unit except for the semiconductor layer and its periphery is covered by a light-shielding layer. Malfunction or reduced sensitivity of an ambient light photosensor due to light from backlights is prevented with a simple structure.