1. An image processing apparatus which processes a plurality of tomograms obtained by acquiring, along a direction crossing at a right angle a section along a thickness direction of a retina, a plurality of tomograms each including the section, comprising: A detection unit configured to detect a layer structure in the retina from image information of respective lines of the tomograms along the thickness direction; an appending unit configured to append structure information to the respective lines based on the layer structures detected for the respective lines; and a mapping unit configured to map 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.