1. An image processing apparatus comprising: a start/end image setting unit configured to set a start image and an end image among a plurality of images which were time-sequentially obtained; an image selecting unit configured to select a plurality of images, as selection images, among the images within a range from the start image and the end image; a conformity calculating unit configured to calculate, as a conformity, at least one of image qualities of the selection images and similarities among the selection images; a conformable image determining unit configured to determine, as a conformable image, the selection image having the predetermined conformity; and a detecting unit configured to detect corresponding positions in the start image and the conformable image and detect corresponding positions in the conformable image and the end image.