In a method for controlling a drafting device of a spinning frame, the drafting device includes a front bottom roller 12, a middle bottom roller 13, a back bottom roller 14, and motors (15, 16a, 16b, 17a, 17b) that independently drive the bottom rollers. The method includes changing a break draft ratio of the drafting device in a deactivation process of the spinning frame so that a load torque of the drafting device is smaller than when the break draft ratio is set to a value for normal operation to limit untwisting of the bottom rollers. The method further includes changing a main draft ratio when a fiber bundle, which has passed by the middle bottom roller 13 during a period the break draft ratio is changed, passes by the front bottom roller 12, to cancel influence on the fiber bundle of the changing in the break draft ratio.