An image signature creating method includes: creating a map by partitioning a still image using rings defined by concentric circles radially spaced apart from each other by a predetermined interval and radial lines circumferentially spaced apart from each other by a predetermined angle, the center of the still image being that of the concentric circles; and creating an image signature from the created map on the basis of distribution of pixels in regions defined by the rings and the radial lines. Accordingly, distribution of illegal contents is prevented and interrupted by search for and discrimination of a still image illegally deformed by a copying of or an intended attack on the still image.