Two or more sensing switches are included in a sensing unit for detecting a characteristic value of a subpixel, and are electrically coupled to a reference voltage line. The two or more sensing switches share a sampling switch with a sensing capacitor included in the sensing unit, which reduces size of the sensing unit. Sensing may include driving simultaneously two or more sensing switches sharing a sensing capacitor, or sensing may be performed through continuous and short driving after simultaneous driving. Overall sensing time can be reduced and sensing accuracy improved.