To provide a radiation CT apparatus capable of controlling the quantity of focal shift according to conditions for radiography.

The radiation CT apparatus includes a radiation source for applying radiation to a subject; a radiation detector disposed facing the radiation source for detecting the radiation penetrating the subject; a scanner with the radiation source and the radiation detector mounted therein to rotate around the subject; an image reconstruction device for reconstructing the tomogram of the subject based on the quantity of penetrating radiation detected by the radiation detector; an image display device for displaying the tomogram reconstructed by the image reconstruction device; a control table to be used for setting the conditions for radiography; and a radiation focal shift device for shifting the focus of the radiation in the direction of rotation of the scanner or in the direction of the rotation axis. The radiation CT apparatus further includes a radiation focal shift quantity control device for controlling the quantity of focal shift of radiation based on the set conditions for radiography.