PURPOSE: To dispense with a packing by mounting the first and second feed parts composed of feed screws fitted to each other and providing the outer end of a charge port of each material to the inside position of the screw thread of each feed part.

CONSTITUTION: The materials charged from material charge ports 13, 14 are respectively fed to the central part in succession by feed screws 21c, 22c, 21d, 22d to be kneaded by blades 21a, 22a, 21b, 2b and extruded to the outside from a material discharge port. Since the materials are charged inside at least two screw threads of the feed screws 21c, 22c, 21d, 22d, even when the materials escape toward both ends of cylinders 11, 12, they are returned to the central part. By this constitution, a packing is dispensed with at a place where rotor shafts 11, 12 the wall body of a casing 1 and maintenance can be made free.