To provide a method of producing a polyester composition excellent in impact resistance.

In the method of producing a polyester composition: a composition raw material including 65-95 pts.wt. of a polyethylene terephthalate and 5-35 pts.wt. of a hydrogenated styrene/conjugated diene block copolymer with weight-average molecular weight of 200,000-800,000 is heated and kneaded at a shear rate of ≥500 s^-1 in a temperature range of 250-300°C. In particular, the hydrogenated styrene/conjugated diene block copolymer is a styrene-ethylene-butylene-styren block copolymer.