The present invention relates to an electronic watermark burying device that does not bury the same electronic watermark data in a superimposing mode. An electronic watermark insertion device comprises discrete cosine transforming means for subjecting an input image into a discrete cosine transformation; electronic watermark burying means for inserting electronic watermark data to data transformed by the discrete cosine transforming means; electronic watermark detecting means for detecting whether or not the electronic watermark data to be inserted by the electronic watermark burying means has been already inserted into the input image; and selecting means for selecting the output data from the discrete cosine transforming means when the electronic watermark detecting means detects that the electronic watermark data has been already inserted into the input image or for selecting output data from the electronic watermark burying means when the electronic watermark detecting means does not detect that the electronic watermark data has been not inserted into the input image; and means for subjecting data selected by the selecting means into an inverse discrete cosine transformation.