Polyester resin particles are provided as those capable of providing a highly transparent molded product by thermoforming, while suppressing fusion of the polyester prepolymer particles in a heat treatment thereof such as crystallization or solid-phase polycondensation, without reduction in a solid-phase polycondensation rate.The present invention provides a method for producing a polyester resin, comprising carrying out a hot-water treatment and a heat treatment, in this order, of polyester prepolymer particles obtained by melt polycondensation of a dicarboxylic acid component and a diol component. The hot-water treatment comprises bringing the polyester prepolymer particles with an intrinsic viscosity of from at least 0.10 dL/g to at most 1.0 dL/g and with a density of at most 1.36 g/cm3 into contact with hot water at a temperature higher than the glass transition temperature of the polyester prepolymer particles and less than 100° C., under the condition satisfying the following formula (1): 40≦(T−Tg)t≦6000  (1) wherein t is a hot-water treatment time (second), T is the temperature of the hot water (° C.) and Tg is the glass transition temperature (° C.) of the polyester prepolymer particles.