The present invention relates to a display device in which a plurality of optical sensors are provided in a display panel. A liquid crystal panel with built-in sensors (11) includes, in a pixel array (18), a plurality of pixel circuits and a plurality of optical sensors which are arranged two-dimensionally. A panel drive circuit (17) writes signals generated according to display data D3 into the pixel circuits, and reads signals generated according to the amounts of received light, from the optical sensors. An image processing unit (12) switches display data which is used before reading by the panel drive circuit (17) is performed, to fixed data suitable for image input. For the fixed data, white image data or blue image data is used. According to the present invention, by performing image input after displaying, using fixed data, an image suitable for image input, the influence of a displayed image is eliminated, enabling to perform image input and touch position detection with high accuracy, irrespective of displayed image. The display device of the present invention can be used as a liquid crystal display device.