An X-ray CT imaging device for performing X-ray CT imaging of a CT imaging area of a subject, the X-ray CT imaging device comprising: an imaging mechanism including an X-ray generator for generating X-ray, an X-ray restriction section (13, 14, 15) for blocking and restricting a radiation range of the X-ray generated by the X-ray generator to form an X-ray cone beam to be directed to the CT imaging area, and an X-ray detector for detecting the X-ray cone beam directed to the subject; a support for supporting the X-ray generator and the X-ray detector in the state where the X-ray generator and the X-ray detector have the subject therebetween; an imaging mechanism driving section (37, 41) for revolving the support at least about an axis of a revolution shaft with respect to the subject; and a control section for controlling at least the X-ray generator, the X-ray restriction section (13, 14, 15) and the imaging mechanism driving section (37, 41); wherein: a direction parallel to a direction of the axis of the revolution shaft is a length direction; and the X-ray restriction section (13, 14, 15) includes: a length direction X-ray blocking section (14, 14a, 14b) for blocking and restricting the radiation range of the X-ray cone beam in the length direction with respect to the CT imaging area; and a length direction adjusting section for, during the X-ray CT imaging when the support is revolving, adapting an expansion in the length direction of the X-ray cone beam, which is to be restricted by the length direction X-ray blocking section (14, 14a, 14b), to a height of an edge of the CT imaging area on a X-ray generation section side of the CT imaging area in accordance with a revolution position of the imaging mechanism driven by the imaging mechanism driving section (37, 41), the length direction adjusting section being controllable by the control section. an imaging mechanism including an X-ray generator for generating X-ray, an X-ray restriction section (13, 14, 15) for blocking and restricting a radiation range of the X-ray generated by the X-ray generator to form an X-ray cone beam to be directed to the CT imaging area, and an X-ray detector for detecting the X-ray cone beam directed to the subject; a support for supporting the X-ray generator and the X-ray detector in the state where the X-ray generator and the X-ray detector have the subject therebetween; an imaging mechanism driving section (37, 41) for revolving the support at least about an axis of a revolution shaft with respect to the subject; and a control section for controlling at least the X-ray generator, the X-ray restriction section (13, 14, 15) and the imaging mechanism driving section (37, 41); wherein: a direction parallel to a direction of the axis of the revolution shaft is a length direction; and the X-ray restriction section (13, 14, 15) includes: a length direction X-ray blocking section (14, 14a, 14b) for blocking and restricting the radiation range of the X-ray cone beam in the length direction with respect to the CT imaging area; and a length direction adjusting section for, during the X-ray CT imaging when the support is revolving, adapting an expansion in the length direction of the X-ray cone beam, which is to be restricted by the length direction X-ray blocking section (14, 14a, 14b), to a height of an edge of the CT imaging area on a X-ray generation section side of the CT imaging area in accordance with a revolution position of the imaging mechanism driven by the imaging mechanism driving section (37, 41), the length direction adjusting section being controllable by the control section. a direction parallel to a direction of the axis of the revolution shaft is a length direction; and the X-ray restriction section (13, 14, 15) includes: a length direction X-ray blocking section (14, 14a, 14b) for blocking and restricting the radiation range of the X-ray cone beam in the length direction with respect to the CT imaging area; and a length direction adjusting section for, during the X-ray CT imaging when the support is revolving, adapting an expansion in the length direction of the X-ray cone beam, which is to be restricted by the length direction X-ray blocking section (14, 14a, 14b), to a height of an edge of the CT imaging area on a X-ray generation section side of the CT imaging area in accordance with a revolution position of the imaging mechanism driven by the imaging mechanism driving section (37, 41), the length direction adjusting section being controllable by the control section. a length direction X-ray blocking section (14, 14a, 14b) for blocking and restricting the radiation range of the X-ray cone beam in the length direction with respect to the CT imaging area; and a length direction adjusting section for, during the X-ray CT imaging when the support is revolving, adapting an expansion in the length direction of the X-ray cone beam, which is to be restricted by the length direction X-ray blocking section (14, 14a, 14b), to a height of an edge of the CT imaging area on a X-ray generation section side of the CT imaging area in accordance with a revolution position of the imaging mechanism driven by the imaging mechanism driving section (37, 41), the length direction adjusting section being controllable by the control section.