A pixel array substrate including a substrate, a plurality of display pixels, a plurality of sensing pixels, and a read-out circuit is provided. The substrate includes a first region and a second region. The second region is located between the first region and an edge of the substrate. The display pixels are disposed on the first region and the second region of the substrate. The sensing pixels are disposed on the first region of the substrate. The read-out circuit is electrically connected to the sensing pixels. A portion of the read-out circuit is disposed on the second region of the substrate and the portion of the read-out circuit is located between two display pixels of the display pixels.