The present invention provides a disk unit suitable for recording and reproducing time-series continuous data such as AV data.When data received as data to be written into recording medium is audio and/or video data, (this data is called AV data hereinafter), address information 403c identifying a beginning sector of the recording medium in which the data has been written is registered in file control information 402. Also, it is determined whether or not the AV data is contiguous with AV data just before written. If it is contiguous, the beginning sector is not registered in control information storage means. Thus continuous data can be handled as one piece of data.