A plurality of images of a plurality of sections in an object are processed by using a ROI-specifying unit to specify a three-dimensional (3D) ROI (region of interest) at a region to be targeted in a three-dimensional space formed by the images. A deciding unit is then used to select one or more sections crossing the three-dimensional ROI, and a display unit is used to display images of the selected sections. The image of each of the selected sections includes an area crossing the 3D ROI. The ROI-specifying unit operates to place the 3D ROI at a region to be targeted on a first image of a section and three-dimensionally locates the 3D ROI at the region to be targeted by using both the first image and a second image of another section.