A display device includes a substrate including a display area, a peripheral area outside the display area, and a pad area within the peripheral area; a testing circuit unit disposed within the pad area; a cover layer covering the testing circuit unit; an output pad disposed within the pad area and arranged between the testing circuit unit and the display area; an input pad disposed within the pad area, disposed at an opposite side with respect to the plurality of output pads; and a protective layer covering the output pad and the input pad, and, on a plane, an end of the protective layer is apart from the cover layer.