A medical image-processing apparatus that corrects divergence, even in a case where divergence in CT numbers occurs throughout a plurality of sets of image data that have been acquired for anatomically identical areas because the observed object is undergoing shape-alteration. The apparatus includes an image data storage, an extractor, and a corrector. The image data storage stores respective sets of image data acquired by scanning a targeted region undergoing chronological shape-alteration in a subject, the scanning having been executed at predetermined respective timings. The extractor extracts image data that correspond to the targeted region out of each of the respective sets of image data. The corrector calculates degrees of shape-alteration of the targeted region in the respective extracted sets of images data and to correct CT numbers of the respective sets of image data extracted for the targeted region, based on calculated degrees.
