In one embodiment, an X-ray CT apparatus includes: an X-ray detector equipped with a plurality of detection elements each of which is configured to output an X-ray signal in accordance with X-rays passing through an object; and a scan controller configured to acquire X-ray signals in each of a first mode and a second mode in one scan by switching between the first mode and the second mode, the first mode being a mode of acquiring high-resolution data which are respective X-ray signals outputted from the plurality of detection elements, the second mode being a mode of acquiring normal-resolution data in which X-ray signals outputted from some of the plurality of detection elements are integrated.