To interweave a cord string for indicating the use limit based on abrasion and damage without any increase in thickness of a twill woven belt sling itself.

A cord string 12 is inserted between a twill weave column B and its adjacent twill weave column B, and between an upper part 14a of a weft 14 and a lower part 14b of the twill weave column B itself. In the twill weave column B, a space portion is necessarily formed between the upper part 14a and the lower part 14b so that even if the cord string 12 is inserted therein, a belt sling is not increased in thickness. That is, the thickness of the twill weave column B is exclusively determined by the number and thickness of warps 13 and wefts 14 constituting the twill weave column. When the belt sling is in the normal state, the cord string 12 is not seen from the outside, but when the belt sling is worn away or damaged so that the cord string 12 is exposed, it is taken as a measure of the use limit.