A flame retardant polyester fiber for artificial hair, which is obtained by melt spinning a composition as a mixture of 100 parts by weight of (A) a polyester made of one or more of polyalkylene terephthalate and a copolymer polyester comprising polyalkylene terephthalate as a main component with 5 to 30 parts by weight of (B) a brominated epoxy flame retardant. The present invention also relates to the polyester fiber for artificial hair which has at least one modified cross-section, is a mixture with a fiber having a modified cross-section, and has a mixing ratio of the fiber having a round cross-section to the fiber having a modified cross-section is 8:2 to 1:9, and to the flame retardant polyester fiber for artificial hair which further comprises a hydrophilic fiber treating agent attached thereto, and thus has excellent smooth feeling, combing properties, and flame retardance.