An audio signal is compressively encoded into encoding-resultant audio data. A video signal is compressively encoded into encoding-resultant video data. An audio time stamp for audio-vide synchronous reproduction is added to every unit of the encoding-resultant audio data. A video time stamp for audio-video synchronous reproduction is added to every unit of the encoding-resultant video data. The time-stamp-added audio data and the time-stamp-added video data are multiplexed into main data. To a plurality of first after-recording-purpose data for at least one of (1) the encoding-resultant audio data and (2) the encoding-resultant video data which form the main data, time stamps for reproduction synchronous with a portion of the main data and identification information for identifying the plurality of first after-recording-purpose data are added to convert the first after-recording-purpose data into second after-recording-purpose data. The second after-recording-purpose data are made into bit streams without being multiplexed with the main data.