To provide a method for granulating a copolyester resin which can rapidly correspond to the change of the melting viscosity of the copolyester to reduce the load on a pulverizer, caused by the change of the melting viscosity of the resin, and by which the granulation time can be shortened.

This method for granulating a copolyester resin comprising cooling and solidifying a molten extruded copolyester resin, and pulverizing the cooled copolyester comprises connecting a pipe for blowing an inert gas into a pipe for transferring the copolyester resin, present between a polycondensation reaction vessel and a discharging nozzle, calculating the amount of the inert gas for the best blowing from the detected value of the melt viscosity of the copolyester resin by a computer, and automatically changing the opening of a valve for supplying the inert gas so that the blowing amount of the inert gas may become the best amount.