PURPOSE: To provide the titled compsn. having improved toughness, consisting of polyethylene terephthalate having a specified compd. unit, an aliph. polyester, an α-olefin/α,β-unsaturated acid glycidyl ester copolymer and glass fiber.

CONSTITUTION: A polyethylene terephthalate (A) having an intrinsic viscosity of 0.3 or above, composed of at least 80mol% of ethylene terephthalate repeating unit and 0.05W5wt% compd. of formula I or II (wherein M, M' are each an alkali metal; n, m are each 1, 2) is blended with 1W10wt% aliph. polyester (B) having an MW of 2,000 or above, obtd. by reacting a dibasic acid component consisting of adipic acid and/or sebacic acid with a glycol component, 1W50wt% copolymer (C) of an α-olefin (e.g., ethylene) with 1W50wt% glycidyl ester of an unsaturated acid of formula III (wherein R is H, a lower alkyl which may be substituted with glycidyl ester group) and 5W60wt% glass fiber (D) having a diameter of 8W14μm and a length of 3W6mm.