<p>An image identity scale calculating system capable of calculating an identity scale indicating the degree to which two images are identical in consideration of the balance between the identification ability and the robustness. An image feature amount comparing means (2A) determines hierarchical quantization index codes of an encoding format capable of uniquely identifying quantization indexes of a plurality of hierarchies calculated by hierarchically performing quantization for each area to be quantized in the two images according to a predetermined hierarchical quantization method as input, and selects a set of quantization indexes used for comparison as a comparison quantization index set according to information separately given. The image feature amount comparing means (2A) compares the hierarchical quantization index codes of the two images and calculates the identity scale of the two images by using the comparison quantization index set.</p>
