<p>Provided is a radiation tomography device (9) which can suppress the number of mounted radiation detectors and be manufactured at low cost. One of the detector rings (12) is a first detector ring (12a) having a sufficient inner diameter for introducing the shoulders of a test subject M. Another one is a second detector ring (12b) having a smaller inner diameter than the first detector ring (12a). Thus, an inexpensive radiation tomography device (9) which can limit the number of radiation detectors (1) comprising a detector ring (12) can be provided. In addition, if the diameter of the detector ring (12) can be smaller, both the spatial resolution of the radiation and the detection sensitivity improve.</p>
