Provided is an image processing apparatus, etc., that can accurately determine whether there are abnormal villi even if one image includes regions with different imaging distances to an object. An image processing apparatus 1 includes a region-of-interest setting unit 110 that sets a region of interest in an image a linear convex region extracting unit 120 that extracts, from the region of interest, a linear region having a predetermined number or more of continuously-arranged pixels whose pixel values are higher than those of their neighboring pixels an intra-region curvature feature data computing unit 130 that computes curvature feature data based on curvatures of one or more arcs along the linear region and an abnormality determining unit 140 that determines whether there is an abnormal portion in the region of interest, based on a distribution of the curvature feature data.
