To provide a method and a device for producing fine particles of molten resin by mixing carbon dioxide to the molten resin so as to lower viscosity and spraying the mixture into the atmosphere.

In a method for pulverizing molten resin by injecting molten resin continuously supplied under high pressure and high temperature and high pressure carbon dioxide to the atmosphere from the high pressure condition, when a fluid A and a fluid B are any of carbon dioxide and the molten resin, a multi-stage division flow passage type mixer is used as a mixer, which has a fluid A division part for evenly dividing the fluid A after the fluid A flows into the mixer, a fluid B division part for evenly dividing the fluid B after the fluid B flows into the mixer in the downstream side of the fluid A division part, a double tube type mixing part constituting a cylindrical double tube type mixer structure having the fluid A as the inner fluid and the fluid B as the outer fluid in the downstream side of the fluid B division part, and an individual contraction part for contracting an outlet of the double tube type mixing part in the downstream side of the double tube type mixing part. A pulverizing process of the resin and a product thereof can be provided.