An image signature to be used for matching is generated by the following generation method. First, region features are extracted from respective sub-regions of a plurality of pairs of sub-regions in an image, and for each of the pairs of sub-regions, a difference value between the region features of two sub-regions forming a pair is quantized. Then, a collection of elements which are quantization values calculated for the respective pairs of sub-regions is used as an image signature to be used for discriminating the image. The image signature matching device specifies, from an image signature of a first image and an image signature of a second image generated by the above generating method, a margin region of each of the images. The image signature matching device matches the image signature of the first image and the image signature of the second image in such a manner that a weight of an element, in which at least one of two sub-regions forming a pair is included in the specified margin region, is reduced.