An array substrate for an X-ray detector and an X-ray detector including the reduces or minimizes a leakage current caused by etching of a PIN layer, and also reduces or minimizes light reaction of the PIN layer within a non-pixel region. The array substrate for the X-ray detector includes an integrated PIN layer formed to cover all pixel regions. Upper electrodes, which are spaced apart from each other according to individual pixel regions, are disposed over the PIN layer. A light shielding portion is disposed between neighboring upper electrodes.