PURPOSE: To simply produce a thermoplastic resin multilayered sheet or film by extruding a separate thermoplastic resin film to laminate the same on a thermoplastic resin film and pressing the laminated thermoplastic resin films between a casting drum and an endless belt in the vicinity of a guide roller to mutually weld them.

CONSTITUTION: Thermoplastic resin films successively extruded from three T-dies 13a, 13b, 13c to be stacked are set to a first thermoplastic resin film 16 and a separate T-die 15a extruding a second thermoplastic resin film to the surface of the first thermoplastic resin film 16 is arranged above an inclined running part 12b. A rotatable casting drum 18 pressing the second-thermoplastic resin film to the first thermoplastic resin film 16 to mutually weld, laminate and integrate both films between a metal endless belt 11 and the drum 18 is arranged in the vicinity of the lower metal roller 10c among two metal rollers 10b, 10c positioned at both ends of the inclined running part 12b.