PURPOSE: To improve yarn drawing workability and shorten working time by collectively holding a group of yarns drawn from respective bobbin carriers through an assembling auxiliary device.

CONSTITUTION: An assembling auxiliary device H is detachably mounted on the mandrel supporting device b6 of a mandrel device Bm, the yarn converging guide h7 of the device H is subjected to positioning control in the proximity of the yarn guide member g2 of a yarn guide G, and yarns Y drawn from the bobbins of respective bobbin carriers C are successively passed through the yarn converging guide h7 and their ends are collectively held by a yarn holding member of the device H. Subsequently, the braider body Bb is driven so as to make the respective bobbin carriers C travel along the orbit and the group of yarns Y collectively held at the device H are temporarily interlaced between the yarn converging guide h7 and the supporting plate of the yarn holding member followed by driving halt temporarily, and the yarn group Y is cut at its converged and interlaced part followed by detaching the device H and then driving the braider body Bb again to start an assembling operation.