The purpose of the invention is to reduce the occurrences of the region of interest falling outside of the image due to the effects of respiratory movements or pulsations. In the medical image-processing apparatus, a series of cross-sectional images is generated by an image-generating unit (115) from a series of volume data files pertaining to a three-dimensional region of a subject. Multiple cross-sections that correspond to each of the cross-sectional images are individually determined by a cross-section-determining unit (125) on the basis of the position of the same region contained in the multiple volume data files.