An image-comparing apparatus is provided for comparing a code stream obtained by encoding a retrieved image with a specific image for determining whether the code stream is substantially identical to the specific image. The apparatus includes image-characteristic amount extracting unit for analyzing the code stream to extract an image-characteristic amount of the retrieved image. The apparatus further includes encoding-parameter extracting unit for extracting an encoding parameter from the code stream and encoded-data generating unit for encoding the specific image to some extent, on the basis of the encoding parameter, in order to generate encoded specific-image data. A comparing unit compares the image-characteristic amount of the retrieved image with the encoded specific-image data is also provided to determine whether the code stream is substantially identical to the specific image.