The collecting part of the X-ray CT apparatus according to the embodiment scans a subject using X-rays and collects data. The memory prerecords a basic image including the designated area of the subject. The controller instructs the collector to repeatedly perform the first scan, using the conditions for the first scan, of the designated area of the subject to who contrast agent has been administered. The controller then receives the specified trigger input, and instructs the second scan of the subject using the conditions for the second scan. The image generator repeatedly produces the first medical image based on the data collected when the first scan is being performed, and produces a subtraction image from the first medical image and the basic image. The image generator then produces the second medical image based on the data collected when the second scan is being performed.
