To dissolve defects on surface quality such as willow like wrinkles, bright specs, puckering, etc., caused by heat-treating on using a PTT-based composite fiber as a liner fabric having relatively small texture-restraining force.

This polytrimethylene terephthalate-based conjugated fiber is characterized by comprising a group of single fibers obtained by joining two polyester components side by side or as an eccentric sheath core type and having a polytrimethylene terephthalate as at least one component constituting the single fiber, and satisfying the following (1) to (5) requisites. (1) The elongation rate of apparent crimps before boiling water treatment is ≤20 %. (2) Elongation rate measured after the boiling water treatment by loading 3.5×10-3 cN/dtex is 2-10 %. (3) Dry heat contraction stress value is 0.05-0.24 cN/dtex. (4) Breaking elongation is 30-45 %. (5) Stress values in 10 % elongation in elongation/stress measurements exhibit ≤0.03 cN/dtex difference between the maximum and minimum values along the longitudinal direction of the fiber.