An image processing apparatus includes: a blood vessel sharpness calculation unit configured to calculate blood vessel sharpness representing sharpness of a visible vascular pattern in a mucosa region in which a mucosa in a lumen is shown in an intraluminal image; an abnormal candidate region extraction unit configured to extract a sharpness reduction region in which the blood vessel sharpness is reduced, as a candidate region for an abnormal region in which the visible vascular pattern is locally lost; and an abnormal region determination unit configured to determine whether the candidate region is the abnormal region based on a shape of the candidate region.