A medical image data processing apparatus includes: an imaging unit that has an X-ray tube for irradiating a subject with X-ray and an X-ray detector for detecting X-ray passed through the subject and scans the subject to collect raw data; a reconstruction unit that reconstructs image data from the collected raw data; a cutout unit that calculates, based on an image to be observed selected from the reconstructed image data, an imaging position of the image to be observed and cut outs, from the collected raw data, raw data existing within a previously set range including raw data constituting the image to be observed; and a storage unit that stores the raw data cut out by the cutout unit together with associated additional information.