An X-ray CT apparatus which executes a first X-ray tomography on a sectional plane having a desirable thickness in an object to be examined (0) with the object interposed between an X-ray generator (1) and a two-dimensional X-ray image sensor (2) provided so as to hold their mutual facing positional relation, and also executes a second X-ray tomography for obtaining a CT image of the interested area of the object (0). The first X-ray tomography is executed on the object (0) while the object (0) is held and fixed by an object holder (4) with the center of the orbit of the X-ray circulating radiation fixed, and while the object holder (4) is moved by an object mover (5) along the X-ray sectional image forming path according to the rotary angle of the X-ray circulating radiation.