PURPOSE: To limit a webbing from being suddenly delivered from the side of a retractor at the time of imparting pretension to a seat belt unit.

CONSTITUTION: A delivery limiting means 10, regulating the delivery of a webbing W from a retractor R by operation of a pretensioner P, is interposed between this retractor R and the pretensioner P. When this pretensioner P operates, a mid part of the webbing W is pulled in a loop form and thereby tension acts on both sides retractor side and rider side) in the spreading direction of the webbing W, therefore this webbing W is intended to be rapidly delivered even from the retractor side, but at that time, the webbing W comes into slidingly contact with a delivery limiting means 10 by operation of the pretensioner P, whereby this deliver of the webbing W is regulated by dint of frictional resistance.