1. An information processing apparatus for retrieving image data that is similar to an entered document image, comprising: segmentation unit adapted to segment the entered document image into a plurality of areas on a per-attribute basis; similarity calculation unit adapted to calculate degree of similarity, for every area obtained by segmentation, using retrieval unit suited to the attribute; and overall-similarity calculation unit adapted to calculate overall degree of similarity in which the degree of similarity calculated for every area obtained by segmentation is weighted.