PURPOSE: To stably obtain in a single spin-process self-crimping polyester multifilament yarns excellent in bulkiness, lightweightness and touch feeling having scrolled section.

CONSTITUTION: In producing polyester multifilament yarns ≥90% of which have scrolled section, a polyester is subjected to spinning using a spinneret with scrolled holes consisting of slits each 0.05-0.12mm in width arranged in a direction parallel with one another, the scrolled outermost side of the respective spun yarns are exposed to an air flow at 10-30°C with a velocity of 30-60m/min rectangularly to the filament yarns to effect deviated cooling of the yarns, and the resultant filament yarns are passed through a cylindrical hollow heating device 170-190°C in the internal atmospheric temperature and subjected to noncontact hot drawing and then wound at a speed of ≥3500m/min.