PURPOSE: To change gripping of yarn end part of yarn to be tested from a holding chunk to a holding mechanism and to send the yarn to be tested from the holding mechanism to a knotter.

CONSTITUTION: A great number of holding chucks 6 changeable in holding and releasing are properly set on a vertical face and yarn end par of yarn 5 to be tested is grasped by each holding chuck 6. On the other hand, a knotter 9 and a holding mechanism 8 which is changeable in a knotter position and an opposite approaching position of the holding chuck and is exchangeable in holding and releasing are placed on a moving stand 7, the moving stand is connected to a driving source, is successively movable and changeable from the opposite position of the holding chuck to the opposite position of another holding chuck. Every time the holding mechanism is changed to the opposite position of a given holding chuck, the yarn end part of the yarn to be tested gripped by the holding chuck is changed in gripping to the holding mechanism and guided to the knotter.