1. An image stabilization system, comprising: a region vector detection unit configured to detect a motion vector of each of a plurality of regions in an image; a reliability determination unit configured to determine reliability of the motion vector of each of the regions; a region indicator configured to indicate, to the region vector detection unit, a new detection target region instead of a region whose motion vector is determined to have low reliability; an image vector computing unit configured to compute a motion vector of the entire image using a motion vector determined to have high reliability; and a stabilization unit configured to move an entire image to be output according to the motion vector of the entire image to compensate for sway of the image.