A composite fiber of polytrimethylene terephthalate is composed of a single yarn in which two kinds of polyester components are bonded into a side-by-side type or an eccentric sheath-core type. At least one of the components constituting the single yarn contains 90mol% or more of repeating unit of trimethylene terephthalate. A lay of the composite fiber is wound in a package by the amount of 2 kg or more. The composite fiber is characterized in that 1 the difference between the winding diameter of the lay at the ear part of the package and that at the central part of the package is 10 mm or less, 2 the winding width of the package is 60 to 250 mm and the winding diameter of the package is 100 to 400 mm, and 3 the difference between the dry heat shrinkage stress of the composite fiber wound at the ear part of the package and that at the central part is 0.05 cN/dtex or less.