Abstract: The present invention is concerned with a method and apparatus which blend components of a thermoplastic resin composition in an extruder having a cylindrical body, a screw, and a heating means, wherein the cylindrical body has a large bore part, a tapered part, and a small bore part, and the screw has a large diameter flight, a tapered flight, and a small diameter flight which is fitted within the cylindrical body. The tapered flight has free pass recesses, if desirable, and the roughness of the inner surface of the cylindrical body and/or roughness of the outer surface of the flight of screw are decreased as one proceeds in the direction from the small bore part to the outlet.