An active device array substrate including a substrate, an active device array, a black matrix, a color filter, at least a pad, and at least a contact window is provided. The substrate has a display region and a periphery circuit region. The pad is disposed in the display region or the periphery circuit region and is constituted by at least one of a first conductive layer and a second conductive layer. The contact window is disposed on the pad, through which a third conductive layer is connected to the pad. The contact window is surrounded by at least two different types of light-shielding patterns, wherein each light-shielding pattern surrounds only a part of the periphery of the contact window. The light-shielding patterns are selected form at least two of the black matrix, the color filter, the first conductive layer, and the second conductive layer.