1. An apparatus for processing image information regarding image data pieces each having retrievable information including shooting time and a shooting interval, comprising: a grouping unit configured to group the image data pieces, which are arranged in order of the shooting time, by sequentially carrying out grouping steps that each divide or merge the image data pieces into groups according to the shooting intervals; an evaluation unit configured to calculate a score for each of the grouping steps according to one or a plurality of predetermined evaluation items; and a determination unit configured to determine a specific one of the grouping steps according to the calculated scores.