Abstract: Formation of a partition is quickly performed. Management information areas such as a device area D1, system areas S1 and S2, an optional device area OD1, and the like are produced by writing necessary data, and with respect to a data area, a running amount of a magnetic tape corresponding to its capacity is calculated, and the magnetic tape is made to run by this running amount. Further, also with respect to a search and the like in the case where reproducing/recording is carried out from/to partitions formed in this way, a necessary running amount of the magnetic tape is calculated, and the magnetic tape is made to run by this running amount.