1. An object recognition apparatus comprising: a storage unit configured to store dictionary data in which a plurality of pieces of feature information obtained from a plurality of images of one object are put into groups based on similarities thereof and registered in association with the object; an extraction unit configured to detect an object from an image and, from an image of the object, extract feature information to be newly registered; a selection unit configured to, when the object detected by said extraction unit is registered in the dictionary data, select a group corresponding to the detected object based on a similarity between the extracted feature information and feature information belonging to each group of the detected object; and a registration unit configured to, when said selection unit has selected the corresponding group, register the extracted feature information in the corresponding group of the dictionary data, and when said selection unit has not selected the corresponding group, add a new group to the detected object in the dictionary data and register the extracted feature information.