A novel liquid crystal display device (LCD) including a touch sensor. The LCD includes a first substrate and a second substrate, which face each other, and a liquid crystal layer. The first substrate is provided with a pixel electrode. The second substrate is provided with a first electrode, a second electrode, and an insulating layer. The pixel electrode overlaps with the first electrode with the liquid crystal layer interposed therebetween. The second electrode overlaps with the first electrode with the insulating layer interposed therebetween. The LCD generates a signal corresponding to a potential of the second electrode. This structure enables a thin and lightweight LCD.