To obtain a webbing which uses polyester multi-filament yarns comprising fine single filaments and used for highly strong seat belts as warps for the webbing, has a large strength per unit warp number, is thin and light, and maintains abrasion resistance.

This webbing having a highly large strength per unit warp number, capable of decreasing the cost of raw filaments, and maintaining abrasion resistance is obtained by weaving new highly sized yarns as warps with polyester multi-filament yarns and/or monofilament yarns as wefts in a belt-like form. The highly sized yarns as the warps are obtained by applying a new extremely low cost twisting treatment not general for conventional seat belts to fine single filament polyester multi-filament yarns essential for enabling to spin the filaments in the maximum drawing ratio in a process for producing the polyester filaments for new highly strong seat belts.