A method of manufacturing an X-ray detector includes: applying a mask having an opening on a substrate on which a plurality of charge detection units are positioned; filling the opening with a paste including a photoelectric conversion material that absorbs X-rays to generate charges; and forming a photoconductive layer from the paste by separating the mask from the substrate. A thickness of the paste within the opening is thicker in an area adjacent to at least one edge among edges of the opening than in areas around other edges.