Abstract: A pelletizer of the type of an underwater cutter has its die surface composed of a surface of rotation, e.g., a right circular cylinder, a frustum of a cone, etc., whereby plastic resin materials fed from an extruder under pressure to the outside of the die wall are forced to extrude through a number of die nozzles drilled in the wall of the die to be cut into pellets by a cutter which is rotating in front of the die surface and provided with a plurality of cutter blades the outer edge of each of which is disposed in parallel with the die surface leaving a definite, uniform gap therefrom.