1. An image processing apparatus comprising: an extraction unit configured to extract a structure of a tested eye from an OCT image obtained by optical coherence tomography, and configured to extract a structure of the tested eye from an eyeground image obtained by a scanning laser ophthalmoscope or a fundus camera; a calculation unit configured to calculate a reliability degree of the extraction for each of the extracted structures; and a display control unit configured to display the extracted structures superimposed on an image of eyeground according to the calculated reliability.