A display device includes: an array of pixels disposed on a display area; a connection pad disposed on a pad area; a transmission line electrically coupled with the connection pad; and a conductive dummy pattern disposed under the transmission line. A part of the conductive dummy pattern overlaps the transmission line in a plan view. The transmission line transmits a driving signal or a power signal to the array of pixels. The connection pad includes a pad conductive layer electrically coupled with the transmission line, and a passivation layer disposed on the pad conductive layer. The passivation layer covers at least a side surface of the pad conductive layer and defines an opening overlapping the conductive dummy pattern and the transmission line in the plan view.