The present invention aims to provide a practical polyester that can be produced substantially without using an antimony compound as a polycondensation catalyst. (I) The present invention provides a polyester resin composition containing, on a weight basis, 30 ppm or less of antimony, 0.5 to 50 ppm of titanium, and 0.1 to 100 ppm of phosphorus, in which the number density of titanium-containing particles, the equivalent circular diameter of which is 1 μm or more, is less than 100 / 0.02 mg; and (II) The present invention provides a polyester resin composition containing, on a weight basis, 30 ppm or less of antimony, 0.5 to 50 ppm of titanium, and 0.1 to 100 ppm of phosphorus, in which organic polymer particles are contained in amount of 0.1 to 5 wt %, the organic polymer particles having an average particle diameter determined by dynamic light scattering of 0.05 to 3 μm and containing 0.01% or less of coarse particles relative to the total number of the particles, the coarse particles having a diameter at least twice the average particle diameter.