An image processing apparatus includes: a gradient information calculating unit that calculates gradient information of each of pixels, based on pixel values of an intraluminal image a closed region creating unit that, based on the gradient information, creates a closed region satisfying a condition where the closed region does not include, on the inside thereof, any pixel of which the gradient strength is equal to or higher than a predetermined value, and also, the boundary of the closed region does not curve toward the interior of the closed region, with a curvature equal to or larger than a predetermined value and an abnormal part detecting unit that detects an abnormal part from the inside of the closed region.