There are provided an analysis unit that analyzes an input bit stream to output first intermediate data and analysis information, a conversion rule storage unit that stores a conversion rule, according to which an error-detected bit stream included in the analysis information output from the analysis unit or a bit stream including reference information to an image used for a method not supported by a decoding unit is converted into a bit stream decodable by the decoding unit, and a conversion unit that converts the analysis information into second intermediate data according to the conversion rule, as well as the decoding unit that decodes the first intermediate data and the second intermediate data output from the analysis unit and the conversion unit. Thus, even when the decoding unit does not cope with specific information included in the analysis information, the decoding unit is able to stably perform a decoding procedure.