An image processing apparatus processes a plurality of tomograms obtained by acquiring, along a direction crossing at a right angle a section along the thickness direction of a retina, a plurality of tomograms each including the section. The apparatus detects a layer structure in the retina from image information of respective lines of the tomograms along the thickness direction, and appends structure information to the respective lines based on the layer structures detected for the respective lines. The image processing apparatus maps the structure information of the respective lines of the plurality of tomograms onto a plane crossing the thickness direction at a right angle, thereby generating a two-dimensional image based on the structure information.