PURPOSE: To detect a last position without an END mark by deciding that a block to record the data is a final recording block when the block continues in which the prescribed number of data is not continuously recorded.

CONSTITUTION: A directory area 11b is the area to record the main data contents of the directory, for example, a file name, a date, a file size, etc. For an EOT address area 11, the track number of a final recording track EOT of a main data storing part at the time of recording the directory is recorded. When for example, data of five tracks are not recorded continuously in the track where the data are to be recorded, the track is made into an EOT. Consequently, without recording the data to show a final position like an END mark, the final position of the recorded block can be detected.