PURPOSE: The titled fiber that is composed of polyethylene terephthalate containing polyalkyl ether and an organic sulfonate metal salt and has specific peak temperature of tangential angle loss and specific small-angle X-ray scattering, thus showing good antistatic and fibrilation-resistant properties.

CONSTITUTION: The objective polyester fiber contains (A) 0.6W5wt%, based on the total fiber weight, of polyalkyl ether such as polyethylene oxide and (B) 0.2W3wt% of an organic sulfonic acid metal salt such as sodium stearylsulfonate and shows streaks in the shape of letter "X" on the diagonal lines and/or 2 spot diffraction pattern on the meridional line in small-angle X-ray scattering and lower than 120°C in the peak temperature of tangential angle loss. The cross section of the resultant fiber preferably has a hollow part.