An image processing apparatus includes an image acquiring unit that acquires an in-vivo image being a captured image of an inside of a body cavity; a feature-data calculating unit that calculates feature data corresponding to a pixel or an area in the in-vivo image; a body-tissue extracting unit that extracts, as a body tissue, a pixel or an area whose feature data corresponds to a predetermined threshold; a criterion creating unit that creates a criterion for detecting a detecting object based on the feature data of the body tissue; and a detecting unit that detects a body tissue corresponding to the criterion as the detecting object.