A display device includes: a substrate including, in a plan view, a first area and a second area; a first sub-pixel disposed on the substrate, the first sub-pixel including an emission area disposed in the first area; a second sub-pixel disposed on the substrate, the second sub-pixel including an emission area disposed in the second area; a transmission area disposed on the substrate, the transmission area being adjacent to the second sub-pixel disposed in the second area; and a sensor disposed under the substrate, the photo sensor disposed in the second area. The emission area of the first sub-pixel has a first size and the emission area of the second sub-pixel has a second size different from the first size.