Large-scale X-ray detectors and methods of manufacturing the same are provided, the large-scale X-ray detectors include a photoconductor layer configured to generate electrical charges according to an incident X-ray using an entire area of the photoconductor layer, a common electrode on an upper surface of the photoconductor layer, a plurality of pixel electrodes, configured to convert the electrical charges into electrical signals, on a lower surface of the photoconductor layer and divided into a plurality of groups, and a plurality of application-specific integrated circuits (ASICs) each corresponding to one of the groups. Each ASIC is configured to process the electrical signals conveyed via the pixel electrodes in the corresponding group. The ASICs process the electrical signals so that seamless image information is collectively generated by the ASICs with respect to the entire area of the photoconductor layer.