A digital watermark embedding apparatus of the present invention includes:
a block dividing unit for dividing an input image into plural pixel
blocks; a digital watermark information spreading unit for obtaining an
embedding series having a length corresponding to a number of divided
pixel blocks; a block-by-block embedding unit for selecting at least a
frequency from predetermined plural frequencies according to a term value
of the embedding series corresponding to a position of a pixel block in
the image, amplifying amplitude of a waveform pattern corresponding to
the selected frequency with an embedding strength value, and
superimposing the waveform pattern in which the amplitude is amplified on
the pixel block; and an image outputting unit for outputting an image on
which a corresponding waveform pattern is superimposed on each pixel
block by the block-by-block embedding unit.