An X-ray CT apparatus includes: an X-ray detector in which detecting elements that detect X-rays are arranged in a body-axis direction and a rotation direction； an acquiring unit that acquires signals of the X-rays detected by at least one group of detecting elements which includes a predetermined quantity of detecting elements and in which detecting elements are arranged in at least the rotation direction and that, when reading the signals detected by the detecting elements arranged in the rotation direction from the X-ray detector, sequentially reads the signals at times that vary among the detecting elements arranged in the rotation direction； a correction signal acquiring unit that, in accordance with the signal reading times, acquires correction signals used in a correcting process performed when an image is generated； and an image generating unit that generates the image by applying each correction signal to a corresponding one of the signals.
