In a magnetic disk memory device, the shifting speed of the magnetic head in time of power supply interruption is detected, and a voice coil motor is controlled in accordance with the detected shifting speed to enable the head to be shunted safely and promptly. In a magnetic disk memory device having a spindle motor for revolving a magnetic disk, a magnetic head for reading information from the magnetic disk, a voice coil motor for shifting this magnetic head, and a voice coil motor drive circuit for controlling the drive current of the voice coil motor, the shifting speed of the head in time of power supply interruption is detected on the basis of the back electromotive force generating on the coil of the voice coil motor in time of power supply interruption, there are further provided a retract control circuit for generating a current command value for the voice coil motor drive circuit on the basis of the result of detection and a booster circuit for boosting a voltage resulting from the rectification of the back electromotive force generating in the coil of the spindle motor, wherein the voice coil motor drive circuit and the retract control circuit are operated with the voltage boosted by the booster circuit in time of power supply interruption to control the current to be made to flow to the coil of the voice coil motor and thereby to shunt the magnetic head.