A pixel array substrate includes a base, pixel structures, first bonding pads, first wirings, and a first testing element. The pixel structures are disposed on an active area of a first surface of the base. The first bonding pads are disposed on a peripheral region of the first surface. Each of the first wirings is disposed on a corresponding first bonding pad, a first sidewall of the base, and a corresponding second bonding pad. The first testing element is disposed on the active area of the first surface and has a first testing line. The first testing line is electrically connected to at least one of the first bonding pads, and an end of the first testing line is substantially aligned with an edge of the base.