PURPOSE: To obtain a polyester resin composition stable to thermal history applied to the composition during molding process, having excellent moldability and capable of keeping the antistaticity and antioxidation property over a long period and to obtain an antistatic agent for the polyester resin composition.

CONSTITUTION: This antistatic polyester resin composition having excellent thermal stability is produced by compounding 100 pts.wt. of a polyester resin with (A) 0.1-5 pts.wt. of an alkanesulfonic acid alkali metal salt and/or alkanesulfonic acid alkaline earth metal salt, (B) 0.005-5 pts.wt. of a hindered phenolic antioxidant and (C) 0.01-2 pts.wt. of one or more substances selected from synthetic zeolite, synthetic hydrotalcite and basic metal oxide or hydroxide of the group I metal, group II metal of the periodic table or rare earth metal. The antistatic agent is composed of these additives.