An X-ray CT apparatus of the present invention includes: an X-ray source which irradiates X-rays an X-ray detector which is arranged oppositely to the X-ray source and detects the irradiated X-rays a scanner having a rotary disk which rotatably supports the X-ray source and X-ray detector and a power source of the rotary disk an image processing device which makes the scanner rotate in a state where an object is inserted in between the X-ray source and the X-ray detector to irradiate the object with X-rays from directions at a plurality of angles, and makes the X-ray detector detect X-rays transmitted through the object in directions at a plurality of angles as projection data, to reconstruct a tomographic image of the object by the use of the projection data in the directions at the plurality of angles a display device which displays the reconstructed tomographic image a setting device which sets X-ray irradiation condition candidate by at least one combination of a tube current and a tube voltage for power to be supplied to the X-ray source by the use of a transmission thickness of a scanning subject site of the object and a control device which supplies the with an X-ray irradiation condition corresponding to the set X-ray irradiation condition candidate, to perform scanning, and in the X-ray CT apparatus, the setting device sets X-ray irradiation condition candidate by at least one combination of a tube current and tube voltage for power to be supplied to the X-ray source by the use of an X-ray absorption coefficient of said scanning subject site of the object, and the control device makes the display device selectably display each of the set X-ray irradiation condition candidates which is provided for a diagnosis of a requested tissue of the object, to take control such that a tomographic image of the object is taken according to the selected X-ray irradiation condition candidate.
