A feature vector computation section 24 of an image processing apparatus computes a feature vector expressing gradient histograms for each of plural child regions that have been further partitioned from plural parent regions partitioned from a discrimination-subject image. A feature relative vector computation section 26 of the image processing apparatus computes for each parent region a feature relative vector expressing relative values computed from respective combinations of the same or different elements across feature vectors computed for each child region, and relative values computed from respective combinations of the same or different elements within one of the feature vectors. A discrimination section 30 of the image processing apparatus, based on the feature relative vector computed for each parent region, discriminates whether or not the image subject to processing is an image in which a processing target object appears.