In a second grid, X-ray absorbing portions and X-ray transparent portions extending in a Y direction are alternately arranged in an X direction. After the manufacture of the second grid, a defective portion is detected in the second grid. A rectangular area to be cut out is set along the X and Y directions so as to enclose this defective portion. By cutting out the rectangular area, a cutout is formed. A micro grid, which is smaller than the cutout, is fitted into the cutout such that two adjoining sides of the micro grid are in contact with two adjoining sides of the cutout. A gap left between an outline of the cutout and the micro grid is filled with Sn&mdash；Pb as an X-ray absorbing material.
