Polyester false-twist yarn and method of manufacturing the yarn

A polyester false-twist textured yarn comprising a false-twist textured yarn, of a multifilament yarn, comprising a polyester resin,

• wherein cross-sectional profiles of a plurality of individual filaments, from which the false-twist textured multifilament yarn is constituted, satisfy all of the requirements (1) to (3) shown below:
• (1) the cross-sectional profiles of the plurality of individual filaments each have 3 to 6 convexities and 3 to 6 concavities formed between the convexities, and the average number of the concavities having a ratio (H/W) of a largest depth (H) of the individual concavities to a largest opening width of the individual concavities of 0.3 or more is in the range of from 50 to 80% of the total number of the concavities;
• (2) an average flatness factor of the cross-sectional profiles of the plurality of individual filaments represented by ratios (L1/L2) of largest lengths (L1) of the cross-sectional profiles of the plurality of individual filaments to largest widths (L2) at right angles to the direction of the largest lengths (L1) is in the range from 1.5 to 3.5;
• and
• (3) a standard deviation of the flatness factors of the plurality of individual filaments is in the range of from 0.3 to 1.0.