PURPOSE: To readily and accurately perform the quality control by disposing a communication device in the robot for traveling along the double twister and performing a doffing treatment and a piecing treatment and monitoring the treatment contents of the robot with the control device of the double twister.

CONSTITUTION: A communication device for communicating treatment contents to the control device 6 of the double twister is disposed in the robot 3 for traveling along the double twister 1 and for performing a doffing treatment and a piecing treatment. Thus, the device permits to monitor the treatment contents of the robot with the monitor 7 of the control device, to accurately know the treatment contents, etc., and to form a graph, etc., necessary for quality control.