PURPOSE: To increase the positioning accuracy of a write/read head for a magnetic tape by storing a waveform correlated with the tape in the direction of length and superimposing the waveform on a control signal.

CONSTITUTION: The movement of a tape 1 running in a driving unit in the direction of intersection is monitored in order to obtain the waveform of the characteristic of the movement of a tape 1 in the direction of intersection and stored in a memory 15 included in the processor 10 of a digital signal. The positioning of a servo head 2A on a servo track ST on a magnetic tape is controlled by a control signal generated by the known track seeking algorithm. The stored waveform is recalled, superposed on the control signal and, thus, the exactitude of positioning of the servo head 2A and the write/read head are sharply increased.