1. An image comparison system characterized by comprising: three-dimensional data input means for input three-dimensional data of an object; reference image storing means for storing a reference image of at least one object; pose candidate deciding means for generating at least one pose candidate as a candidate for pose of the object; comparison image generating means for generating at least one comparison image close to the reference image while projecting the three-dimensional data onto a two-dimensional image in accordance with the pose candidate; and image comparing means for performing comparison on the basis of one of a distance value and a similarity degree between the reference image and the comparison image.