To provide a kneading device for molding a thermoplastic resin, with which the improved dispersant and distributing properties of the resin is obtained and a molded article having a stable and more uniform quality can be obtained.

In a kneading device for molding a thermoplastic resin, within a heating cylinder equipped with a resin feed opening near one end part of which a plurality of rotatable screws 21 and 31 are provided under the state engaging with each other, a notch 24 is provided on each screw flight 22 of one screw 21 and a projecting part 25 is provided in close vicinity to the notch 24 in each screw groove 23 adjacent to the screw flight 22. At the other screw 31, a similar notch 34 and projecting part 35 are provided so as to realize the passing of the notch 24 and the projecting part 25 of the one screw through the projecting part 35 and the notch 34 of the other screw when the screws rotate.