1. An image processing device comprising: a feature data calculator configured to calculate feature data of each pixel in an image or each area acquired by dividing the image into a plurality of areas; an approximate shape calculator configured to calculate an approximate shape approximating a profile of a distribution area in which the feature data is distributed in a feature space having the feature data as an element; and an abnormal area detector configured to detect an abnormal area in the image based on the approximate shape and the profile of the distribution area.