Abstract: This invention provides a technique capable of always keeping digital watermark information embedded in image data having the embedded digital watermark information by an optimum scheme on the basis of a time factor, or removing a digital watermark, or erasing the image data. An apparatus for achieving the above object has functions of holding image data having additional information embedded as a digital watermark, detecting time information related to the image data, and changing the embedding scheme for the additional information as the digital watermark embedded in the image data on the basis of the detected time information.