PURPOSE: To attract the edge of a string positively and shorten cycle time by installing a string detecting device and a pick-finding auxiliary device which interlocks with it on a suction mouth.

CONSTITUTION: An automatic winder consists of a traversing drum 13 which winds a string unwound from a feed bobbin around a winding package 14, an ending device disposed on a string traveling way, a rotatable suction mouth 16 which guides a string edge on the winding package 14 side to the ending device, and a rotatable junction pipe which guides the string edge on the feed bobbin side to the ending device. A string detecting device 30 and a pick-finding auxiliary device 22 which interlocks with the string detecting device are installed on the suction mouth 16, and when the string detecting device 30 does not detect a pick-finding string, the pick-finding auxiliary device 22 starts to operate, and blow-out air flow 23 is blown out from a nozzle 22a to the surface layer 14a of the winding package 14 to loosen the string edge which is twined around the surface layer 14a. When the string detecting device 30 detects the pick- finding string, the pick-finding auxiliary device 22 stops.