To suppress erroneous input in inputting a non-defective product image and a defective product image, thereby increasing accuracy of distinguishing between a non-defective product image and a defective product image. An additional image that is added with an attribute as either one of a non-defective product and a defective product by a user is plotted in a feature space, and the probability that the attribute of the additional image is wrong is estimated. In the case in which the additional image is expected to have a wrong attribute, this result is notified. Result of selection whether to correct the attribute of the additional image by a user who receives the notification is received. A classifier generator 22 determines the attribute of the additional image on the basis of the result of selection and corrects a classification boundary in accordance with the determined attribute.