<p>Disclosed is a liquid crystal display device (100) which comprises a liquid crystal panel (20) including an active matrix substrate (21), an opposing substrate (22), and a liquid crystal layer (23) interposed therebetween and a backlight (10) that emits light to the liquid crystal panel (20). The liquid crystal panel (20) includes a plurality of optical sensor elements (30) that detect intensity of received infrared light. The backlight (10) includes infrared LEDs (light sources; 12) that emit infrared light. Moreover, a surface (100a) of the device is provided with an infrared light transmitting sheet (infrared light partially transmitting portion; 50) that partially transmits infrared light. The optical sensor elements (30) detect positions of input from outside the device by detecting infrared light reflected from an inputting object such as a finger on the surface (100a) of the device. This achieves a liquid crystal display device of the built-in optical sensor type capable of clearly identifying whether or not an inputting object such as a finger is in contact with the surface of the device.</p>
