In a radiation tomography imaging device, the imaging range calculation element 35 calculates a possible imaging range of the FPD 5 based on the imaging distance G, the irradiation swing angle θ and the movable range SP of the X-ray tube 3. The operator can preliminarily calculate the possible imaging range of the radiation detection means prior to the X-ray tomography imaging because the imaging distance, the irradiation swing angle, and the movable range SP are all predetermined parameters. The possible imaging range FP of the FPD 5 is the positional range of the FPD 5 in which the X-ray tube 3 can acquire the X-ray tomography image without moving the X-ray tube 3 to the outside of movable range. Therefore, the radiation tomography imaging can start the X-ray tomography by assuredly moving the FPD 5 within the possible imaging range by referring to the preliminarily calculated possible imaging range of the FPD 5. As results, an incident in which the X-ray tube 3 moves out of the movable range SP and interferes the floor surface W and so forth can be avoided, so that the X-ray tomography imaging can be performed adequately.