The object of the invention is to provide polyester-based fiber which maintains physical properties of usual polyester fiber, such as heat resistance, strength and elongation and is excellent in setting ability with controlled gloss of the fiber, artificial hair using the same, a method of producing polyester-based fiber, and a method of producing artificial hair by using the same. To achieve the object, a composition obtained by melt-kneading polyalkylene terephthalate or a copolymerized polyester (A) based on polyalkylene terephthalate, polyarylate (B) and a phosphite compound (C) is melt-spun to form fiber. In the case of melt-kneading, the ester exchange reaction of components (A) and (B) is prevented due to the inhibitory effect of the component (C) on the ester exchange reaction, the heat resistance and physical properties of the fiber are not deteriorated, and a matte effect is brought about by formation of protrusions on the surface of the fiber.