A magnetic head positioning mechanism positions a magnetic head carried on a carriage at a specific location on a magnetic disc through the movement of a belt mounted to a motor spindle of a step motor. The magnetic head positioning mechanism pulls one end of a belt of which the other end is wound or unwound around a motor pulley, thereby to constantly apply a rotation torque and thereby to eliminate an adverse effect by a dead zone due to the hysteresis phenomenon of the step motor. Alternatively, the rotation torque is always applied to the step motor by pulling the carriage in an access direction, thereby to improve the positioning accuracy of the head.