PURPOSE: To make the degree of wind-up on a bobbin uniform during each doffing step so as to eliminate a difference in length of yarn between doffing steps, by initiating the movement of a ring from a traverse position to the top end part of the bobbin before completion of counting so as to make the position of the ring upon completion of the counting coincident with an arbitrary position on the top end part of the bobbin.

CONSTITUTION: While a ring is moved along a bobbin so as to wind up a yarn fed from a supply roller onto a pirn shape package, the management of the length of a normal yarn which is wound up onto a bobbin is carried out by counting a number of revolutions of the supply roller, and the counting is initiated at the time point when the ring has been shifted to an arbitrary position on the bobbin from a west spool. The shift of the ring from a steady-state traverse position to the top end part of the bobbin is initiated before completion of the counting so that the position of the ring upon completion of the counting is set to be coincident with an arbitrary position on the top end part of the bobbin.