A display device includes a display panel and a signal transmission film including a first extension portion, a second extension portion, and a first dummy pattern. The signal transmission film is connected to one side of the display panel. The first extension portion extends in a first direction, and a first contact hole is formed at a first side of the first extension portion. The second extension portion extends from the first side of the first extension portion in a second direction which is different from the first direction. The first dummy pattern is disposed adjacent to the first contact hole at the first side.