<p>Disclosed is a radiation detector that can reduce insensitive regions even when radiation detectors are densely arranged. The radiation detector fulfills the relationships c = a - (XG1+XG2)/2, d = b - YG1=2e+(n - 2)f, e = b/n - YG1/2, and f = b/n, when: the distance between semiconductor elements (10) that interpose substrates (20) therebetween is XG1; the distance from a semiconductor element (10) on one radiation detector (1) to a semiconductor element (10) on another radiation detector (1) adjacent to the one radiation detector (1) and facing said semiconductor element (10) is XG2; the distance between semiconductor elements (10) arranged in the Y direction is YG1; the horizontal pitch for the semiconductor element pitch (110) is a; the vertical pitch thereof is b; the width of the surface that the radiation from semiconductor elements (10) enters is c; the length thereof is d; the length of a pixel area (10a) inside elements positioned at both end sections of the semiconductor elements (10) is e; and the length of the pixel area (10a) inside a plurality of elements interposed between the pixel areas (10a) inside elements positioned at both end sections of a plurality of semiconductor elements (10) is f.</p>
