The present invention has an object to provide a data processing apparatus which can perform digital watermark embedding/extraction in accordance with manipulation, editing, and compression. To achieve the object, the data processing apparatus for performing compression processing on digital data comprises: a digital watermark extracting device extracting additional information, embedded as a digital watermark, from digital data; a digital watermark removing device removing the additional information, embedded as a digital watermark, from the digital data; an irreversible processing deice performing irreversible processing on the digital data; and a digital watermark embedding device embedding the additional information as a digital watermark in the irreversible-processed digital data.