1. An apparatus for processing image information regarding image data pieces each having retrievable information including shooting, 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 shooting intervals; an evaluation unit configured to calculate a score for each of the grouping steps according to an evaluation item based on a sum of shooting durations of the image data pieces belonging to each group obtained by each of the grouping steps; and a determination unit configured to determine a specific one of the grouping steps according to the calculated scores.