According to a region dividing device, a region dividing member generates a plurality of primary region groups, each of which includes a plurality of primary regions. Each of the plurality of primary regions is characterized by each measured value of feature values. A basic region group generating member generates a single basic region group that includes a plurality of basic regions produced by dividing the target image. Each basic region is characterized by each measured value of feature values. Each measured value is obtained based on the measured values of the plurality of primary regions of the plurality of primary region groups. A region integrating member integrates similar adjacent basic regions into a corresponding integrated region, based on a weighted Euclidean distance between the similar adjacent basic regions.