A liquid crystal display device having an image input function capable of suppressing the degradation of image quality of a display image and a captured image caused by a parasitic capacitance is provided. The liquid crystal display device, which includes an active matrix substrate (1), a counter substrate (2), and a liquid crystal layer and performs inversion driving, includes a photodetection part provided on the matrix substrate (1) for each or at least two of the active elements, and a sensor drive part (5). The photodetection part includes a photodiode and a capacitance storing charge, and outputs a photodetective signal VSOUT whose level changes in accordance with the amount of the stored charge. The sensor drive part (5) outputs, to the photodetection part, a reset signal that resets the charge in the capacitance and a reading signal that causes the photodetection part to output a photodetective signal during a period in which the polarity is set to be a predetermined one, and a current supplied to the active elements does not vary after the completion of the inversion of the polarity.