A display device may include a display panel including a signal pad and a circuit board including a connection pad having a first connection pad portion and a second connection pad portion. The second connection pad portion may be thicker than the first connection pad portion and may not be overlapped with the first connection pad portion in a plan view. The connection pad may be in contact with the signal pad. A first surface roughness between the first connection pad portion and the signal pad may be greater than a second surface roughness between the second connection pad portion and the signal pad.