A disk unit including a control unit for controlling the stop position of a positioning electric motor and positioning a magnetic head operatively linked with the positioning electric motor on a predetermined one of data tracks on a magnetic disk, and positioning error adjustment unit for supplying analog signals to the control unit, wherein the analog signals are related to the positioning error detected by the magnetic head. The control unit includes a control circuit for causing an exciting current which goes high during a time interval T1 and goes low during a time interval T2 during a period T to flow in a first exciting coil of the motor and for causing exciting current which goes low during the same time interval T1 and goes high during the same time interval T2 to flow in another exciting coil adjacent to the first coil, as a function of the magnitude of the aforementioned analog signal; the duration of the time intervals T1 and T2 with respect to the period T is adjusted by the control unit.