A display device includes: a display substrate having a display area and a pad area at one side of the display area; an optical layer on the display area of a first surface of the display substrate; a circuit board on the pad area of the display substrate; and a first sealing material on the pad area of the display substrate to cover the circuit board. The circuit board has: a first portion attached to the first surface of the display substrate, a second portion bent downwardly from the first surface and attached to another surface of the display substrate, and a third portion bent between the first portion and the second portion. The first sealing material covers at least some of the first portion and the third portion.