Abstract: A candidate detection unit 118 detects, for each of a plurality of target images, candidate regions representing a specific detection target region using a discriminator. A region-label acquisition unit 120 acquires, for a part of the target images, position information of a search region as a teacher label. A region specifying unit 121 imparts, based on the part of the target images and the acquired position information of the search region, the position information of the search region to each of the target images, which are not the part of the target images, in semi-supervised learning processing. A filtering unit 122 outputs, for each of the acquired plurality of target images, among the candidate regions, a candidate region, an overlapping degree of which with the search region is equal to or larger than a fixed threshold.