PURPOSE: To obtain superior strength and satisfactorily durable connection by using a bundle piece.

CONSTITUTION: The terminals 1 and 1' of each monofilament are inserted into bundle pieces 2 and 2' respectively. The terminals 1 and 1' are crossed with their mating terminals and then inserted back into the bundle pieces 2 and 2' in the opposite direction, thereby preducing loops 3 and 3' respectively. The monofilaments 4 and 4' on the longer side are then pulled so as to tighten the loops 3 and 3'. After that, the terminals 1 and 1' projected from the bundle pieces 2 and 2' are rotated and are inserted into the openings of the loops 3 and 3'. With this construction, the terminals 1 and 1' are tightly fixed in the loop openings. Therefore, superior connection strength and satisfactorily durable connection can be attained without loosening the connection, even if the tension between the monofilaments on the longer side are released.