section and runs almost the entire width of extrusion mold 1 the inlet 41 for the first resin is at one end of this manifold 3 and clear thermoplastic resin a is fed into the manifold 3 from the resin extrusion apparatus not shown in the figure through first resin feed passage 4 and resin inlet opening 41 when the resin a is fed into the manifold 3 and fills the manifold 3 it moves in the axial direction of the manifold 3 that is in the widthwise direction of the extrusion mold 1 and is extruded from the land 7 to the slit shaped die orifice 6 a thermoplastic resin sheet is extruded with virtually the same width as the manifold 3 the cylindrical inner pipe 2 located in the above manifold 3 is virtually cylindrical said cylindrical inner pipe 2 runs the entire width of the manifold 3 and is located either concentric with the manifold 3 or slightly toward the land 7 the two ends of the cylindrical inner pipe 2 are supported by the side plates 15 16 mentioned above to form the gap 17 between the outer surface of the cylindrical inner pipe 2 and the inner wall of the manifold 3 around the entire circumference one side the previously mentioned resin inlet opening 41 side of cylindrical inner pipe 2 is empty and colored resin feed passage 5 is located here said colored resin.