1. An image signature extraction device, comprising: a first feature extraction unit that extracts, from an image, a first feature corresponding to each of dimensions of a feature vector, the first feature being a quantization value obtained by quantizing a physical quantity extracted from the image; a second feature extraction unit that extracts, from the image, a second feature which is different from the first feature corresponding to each of dimensions of a feature vector; a feature type determination unit that analyzes at least one of the image and the extracted first feature as a subject for analysis to determine whether or not the feature vector constituted of the extracted first features has effectiveness in discriminating an image, and if the feature vector has the effectiveness, determines the first feature to be a type of the feature used for each of the dimensions, while if the feature vector does not have the effectiveness, determines the second feature to be a type of the feature used for each of the dimensions in which the first feature is a predetermined quantization value and determines the first feature to be a type of the feature used for each of remaining dimensions; and a feature vector generation unit that generates a feature vector of the image from the extracted first feature and the extracted second feature according to the determined type of the feature used for each of the dimensions.