1. An image-processing method which searches for a motion vector from between a comparison image and an object image, the method comprising: a calculating operation of calculating a correlation between a reference area on said comparison image and a reference area on said object image while shifting a position of the reference area on said comparison image and a position of the reference area on said object image, wherein said correlation is a correlation between projected data of feature quantities in the reference area on said comparison image and projected data of feature quanities in the reference area on said object image, the projected data of said comparison image is created from a part of a cumulative added image of the feature quantities of said comparison image, and the projected data of said object image is created from a part of a cumulative added image of the feature quantities of said object image.