There are provided a watermark information embedding device and a watermark information detection device which can correctly extract classified information. In the watermark information embedding device, a plurality of dot patterns the wave directions and/or wavelengths of which are changed depending on dot arrangements are prepared, one symbol is given to one of the dot patterns, and the dot patterns are combined and arranged, so that the classified information is given. The watermark information detection device includes two-dimensional wavelet filters the number of which is equal to the number of dot patterns and which have the same wave directions and the same wavelengths as those of the dot patterns. Convolutions between an arbitrary region in a watermarked image and the plurality of two-dimensional wavelet filters are calculated, and it is determined that the dot pattern corresponding to the two-dimensional wavelet filter having the maximum convolution is embedded in the region.