To provide a continuous method for molding a foamed object which can produce foamed plastics only by one extruder with a large apparatus obviated, simplify production equipment, obtain the foamed object by using a raw material containing water with a drying process omitted, and save energy and processes and an apparatus for the method.

An extrusion material comprising the raw material containing water is heated by a heating part 25 between the raw material supply part 5 of a vent type twin-screw extruder 2 and a vent port 9 and melted immediately by a melting disk part 17, and water in the extrusion material is separated by vacuum suction by a vacuum suction part 28 during the heating and melting. After that, liquid carbon dioxide as a blowing agent is supplied from a blowing agent injection port 10 on the downstream side of the vent port 9 into the extrusion material, the extrusion material and the blowing agent are kneaded/ extruded by a kneading/extruding part 32 on the downstream side, and the foamed object of a plastic material is molded continuously from the discharge opening of the extruder 2.