An array substrate for a digital X-ray detector and the digital X-ray detector including the same are disclosed. The array substrate effectively protects a PIN diode from external moisture or water, maximizes a light transmission region of a PIN diode, and reduces resistance by maximizing the region of a bias wiring. To this end, a closed-loop bias electrode formed to cover a circumferential surface of a PIN diode is used. In detail, the bias electrode includes a closed loop portion and a contact extension portion. The contact extension portion extends from one end of the closed loop portion so as to directly contact an upper electrode, and includes a hollow part therein.