NOVELTY - The method involves supplying classified waste plastics into primary and secondary hoppers (3,12) for compressing the volume by internal and external screws (5,14). A rod-shaped object is extruded from the internal screw, which is coated by a doughnut like extruded object from external screws, to form two layer molded structure.    USE - For extruding waste plastics after volume reduction compression to obtain solid fuel.    ADVANTAGE - Even when waste plastics material contains few moisture content, formation of a two layer molded structure reliably and strongly is enhanced. Improves yield of the molded article and enhances transportation and handling. Enhances formation of doughnut like extruded object, as the outer peripheral layer of rod-shaped product firmly and reliably due to the provision of heater to the periphery enclosure of outer side casing and conical nozzle casing. Obtains solid fuel easily, as the inflammable waste plastics is extruded after volume reduction compression.    DETAILED DESCRIPTION - The internal screw is rotatably distributed inside an inner side casing (2) whose one end is opened and the opposite end is connected to the primary hopper. The outer side casing (10) whose one end is opened and the opposite end is connected to the secondary hopper, surrounds the inner side casing. The external screw is rotatably distributed inside the outer side casing and is concentrically arranged along the periphery enclosure of the inner side casing. A conical nozzle casing (11) is provided which is reduced from the end opening of the outer side casing which includes the end opening of the inner side casing. A biaxial screw type extruder (1) moves the extruded product forward after melting compression and extrusion. Heaters (18-20) are provided to the periphery enclosure of the outer side casing and conical nozzle casing. The doughnut-like extruded object is heated and melting solidification of the plastics of an outer surface layer part is carried out. The surface layer obtains the two layer molded structure of a firm waste material. The waste material are inflammable waste plastics. The two layer molded structure is used as a solid fuel.    DESCRIPTION OF DRAWING(S) - The figure shows the entire cross-sectional view of biaxial screw type extrusion machine.    Biaxial screw type extruder (1)    Casings (2,10,11)    Hoppers (3,12)    Screws (5,14)    Heaters (18-20)