A display device includes: a first display area comprising main sub-pixels; a second display area comprising pixel groups spaced apart from each other and a transmission portion between the pixel groups, the second display area having a different resolution from that of the first display area; and extension lines between two pixel groups adjacent to each other in a first direction among the pixel groups and extending in the first direction, wherein each of the pixel groups comprises a plurality of auxiliary sub-pixels and a plurality of horizontal lines electrically connected to the plurality of auxiliary sub-pixels and extending in the first direction, and the extension lines are electrically connected to the horizontal lines included in each of the two pixel groups, and a number of the extension lines is less than a number of the horizontal lines.