To provide an X-ray CT scanner that becomes safer, minimizes the height and the installation space, and is suited for photographing for dental treatment, or the like.

A space 1c for installing a subject 7, a chair 8 and a control device 10 is provided above a shaft-form support structure 1b fixed to a floor. A rotating section 2 holding an X-ray generator 3 and an X-ray detector 4 facing each other by separating the subject 7 by supports 2a and 2b, and carrying and rotating around the subject 7 is rotatably installed in the surroundings of the shaft-form support structure 1b through a bearing. The height and weight of the instrument can be reduced, the installation space can be cut and the structure of the instrument can be made solid. There is no danger of making the head of the subject, an operator, or a worker collide with the instrument, a feeling of compression and blocking can be reduced and the operator can easily approach the subject.