X-ray ct device and contrast imaging method

In order to provide an x-ray CT device and a contrast imaging method which are capable of obtaining an image having a favorable contrast effect without re-injecting a contrast medium, when the imaging position will overtake the contrast medium position during imaging using a contrast medium, this x-ray CT device performs the following: determines whether or not the current imaging position will overtake the contrast medium during the main imaging; resets the imaging conditions when the contrast medium will be overtaken, and executes re-imaging using the reset imaging conditions; and when determining that the contrast medium will be overtaken, performs the determination based on differential data between measurement data obtained by non-contrast imaging performed prior to the main imaging, and measurement data obtained by the main imaging. As a result, it is possible to quickly make an overtaking determination, and immediately move on to re-imaging, without needing to reconstruct an image during the imaging in order to ascertain the presence/absence of a contrast effect.