An X-ray CT apparatus includes: an X-ray source which emits X-rays while rotating around a subject; a compensation filter which adjusts at least one of the output distribution and the spectral distribution of the X-rays emitted from the X-ray source to the subject; an X-ray detector which is disposed opposite to the X-ray source with the subject interposed therebetween, rotates together with the X-ray source, and detects the amount of X-rays transmitted through the compensation filter and the subject; an image operation unit which reconstructs a tomographic image of the subject on the basis of the detected amount of X-rays; a display unit which displays the tomographic image; a control unit which controls each of the constituent components; and a compensation unit which compensates for deterioration of image quality, which is based on the amount of displacement between the rotation center of the X-ray source and a desired position of the subject, by changing an X-ray tube current modulation pattern indicating a time-series change of emission of the X-rays and/or by moving the position of the subject.