A display device which incorporates a touch panel function therein can reduce the number of elements which constitute a photo sensor circuit and can accurately detect an input coordinate position without requiring a particular coordinate arithmetic circuit. In a display device which includes: a display part on which a plurality of pixels are arranged in a matrix array; and a plurality of photo detection circuits which are arranged in a matrix array in the inside of the display part, each photo detection circuit of the plurality of photo detection circuits includes: a photo sensor which converts an incident light into a optical current corresponding to intensity of the incident light; an integral capacitance which integrates the optical current converted by the photo sensor; and a comparator to which a voltage of the integral capacitance is inputted; and the comparator includes a transistor of an open drain output type with a grounded source.
