Disclosed is a tape drive controller (16) that improves data writing performance without impairing the achievement of target data reading rates. When a command processing unit (41) receives a synchronization command, a buffer administration unit (42) hands off data within a buffer to a channel I/O unit (43), and the writing of the data to tape is completed, a backhitch determination unit (44) determines whether to backhitch the tape. If the determination to backhitch the tape is made, a speed setting unit (46) sets a tape speed such that the sum of the time required to write data wherein the backhitch is not involved and the time required to write data wherein the backhitch is involved is the minimum such time, with respect to a range wherein a quantity of data used for purposes of monitoring the achievement of target data read rates is written to the tape. An operation signal output unit (49) instructs that the tape speed be changed to the tape speed thus set, after the tape has been backhitched.