To provide an electronic watermark embedding device for improving accuracy when classified information is being detected. The watermark image forming section 1006 creates a watermark image based on classified information 1004 with reference to the document image. For the document image, embedding regions for embedding a dot pattern which is identifiable as a prescribed symbol by a prescribed filter are detected, and a determination is made as to whether or not the proportion of the text region to the embedding region is less than or equal to a prescribed threshold value, and if the proportion of the text region is less than or equal to the prescribed threshold value, a prescribed number of dot patterns in which a symbol formed of at least a portion of the classified information is identifiable (symbol unit) is embedded in a region where the embedding region and the text region do not overlap. Because classified information is embedded only in regions that do not overlap with the text region by using the document image as a reference, embedding of classified information can be ensured regardless of the form of the original document.