An X-ray CT imaging apparatus (10;110;210) comprising: a turning support (20;124) that supports an X-ray generator (22;126) and an X-ray detector (24;128) such that the X-ray generator and the X-ray detector are opposed to each other with a subject sandwiched therebetween; a turning drive mechanism (30;130) including a turning mechanism (32;132) that turns said turning support about a mechanical turning axis located between said X-ray generator and said X-ray detector, said mechanical turning axis being located closer to the X-ray detector than the center position between the X-ray generator and the X-ray detector, and a turning axis moving mechanism (38; 134) that moves said mechanical turning axis in a direction intersecting with an axial direction of said mechanical turning axis; an imaging region position setting unit (40;151a) that receives a setting of a position of an X-ray CT imaging region with respect to a local part of a dental arch of a head of said subject; and a turning controller (60;151b;251b) that controls said turning mechanism and said turning axis moving mechanism, wherein said turning axis moving mechanism (38;134) moves said mechanical turning axis in synchronization with turning of said turning support (20;124) about said mechanical turning axis using said turning mechanism (32;132), and said turning support (20;124) is caused to perform combined motion during X-ray CT imaging, which allows said X-ray generator and said X-ray detector to turn about said X-ray CT imaging region, and a position of said mechanical turning axis is controlled, in said synchronization, wherein the X-ray CT imaging apparatus is adapted such that a radius of said mechanical turning axis can be changed according to the position of said X-ray CT imaging region set by said imaging region position setting unit. a turning support (20;124) that supports an X-ray generator (22;126) and an X-ray detector (24;128) such that the X-ray generator and the X-ray detector are opposed to each other with a subject sandwiched therebetween; a turning drive mechanism (30;130) including a turning mechanism (32;132) that turns said turning support about a mechanical turning axis located between said X-ray generator and said X-ray detector, said mechanical turning axis being located closer to the X-ray detector than the center position between the X-ray generator and the X-ray detector, and a turning axis moving mechanism (38; 134) that moves said mechanical turning axis in a direction intersecting with an axial direction of said mechanical turning axis; an imaging region position setting unit (40;151a) that receives a setting of a position of an X-ray CT imaging region with respect to a local part of a dental arch of a head of said subject; and a turning controller (60;151b;251b) that controls said turning mechanism and said turning axis moving mechanism, wherein said turning axis moving mechanism (38;134) moves said mechanical turning axis in synchronization with turning of said turning support (20;124) about said mechanical turning axis using said turning mechanism (32;132), and said turning support (20;124) is caused to perform combined motion during X-ray CT imaging, which allows said X-ray generator and said X-ray detector to turn about said X-ray CT imaging region, and a position of said mechanical turning axis is controlled, in said synchronization, wherein the X-ray CT imaging apparatus is adapted such that a radius of said mechanical turning axis can be changed according to the position of said X-ray CT imaging region set by said imaging region position setting unit.