A maximum embedding amount can be ensured depending on information to be embedded, by determining an error-correction capability in correspondence with the characteristic of embedded information. For this purpose, upon multiplexing additional information, the additional information is error-correction encoded. At this time, if the additional information is a BMP file, a WAV file or the like, coding is performed with a low error-correction capability since image reproduction can be made without serious problem even if the error-correction capability is low. The error-correction capability is determined by an error-correction parameter determination unit 205 based on an extension of the additional information.