1. An image processing apparatus comprising: a corresponding point information obtaining unit configured to obtain corresponding point information, which indicates a plurality of pairs of points corresponding on two images, to perform an alignment between the two images; a reliability map obtaining unit configured to obtain a reliability map that indicates a spatial distribution of reliability degrees representing estimated alignment accuracies at a plurality of points of interest on either of the two images, wherein the reliability degree at each point of interest is deduced for that point of interest based on distances between the point of interest and respective corresponding points; a determination unit configured to determine, based on the reliability map, whether the corresponding point information is satisfactory to perform the alignment; and a presentation control unit configured to present the determination result of the determination unit.