1. An image comparison device comprising: a storage in which a model image is stored, the model image including a position of a feature point of a comparison object and a luminance gradient direction at the position of the feature point; a feature amount acquisition unit configured to acquire the position of the feature point and the luminance gradient direction at the position of the feature point from an input image; and an image comparison unit configured to compare the model image and the input image, wherein the image comparison unit performs image comparison by providing an allowable range in both the position of the feature point and the luminance gradient direction at the position of the feature point position.