An abnormality detection unit detects an abnormal object in target images repeatedly acquired. An abnormality type selection unit selects, for each of the target images, an abnormality type of the abnormal object from a plurality of specific abnormality types based on values of at least two basic feature amounts. A feature amount monitoring unit monitors the values of the basic feature amounts and a value of an auxiliary feature amount corresponding to the abnormality type currently selected by the abnormality type selection unit. An adjustment processing unit executes an adjustment process corresponding to the auxiliary feature amount being monitored by the feature amount monitoring unit. The abnormality type selection unit changes the abnormality type to be selected, in accordance with the change in the values of the basic feature amounts mentioned above.