1. An image processing apparatus which processes a plurality of tomographic images obtained by acquiring, along a direction crossing a section along a thickness direction of a retina, a plurality of tomographic images each including the section, comprising: a detection unit configured to detect a predetermined layer in the retina from the plurality of tomographic images; an appending unit configured to append structure information to a region which is a portion of the predetermined layer; and a generation unit configured to generate a two-dimensional image in which the region to which the structure information has been appended is mapped onto a plane crossing the thickness direction.