PURPOSE: To obtain a container, the formability of which is the same as polystyrene resin foamed sheet and heat resistance properties of which are improved by a method wherein the container is formed under the condition that a stretched sheet surface faces inward after heating a laminate arranged with the specified biaxially stretched sheet so as to realize the state that the temperature on the stretched sheet surface side is higher than that on a foamed sheet surface side.

CONSTITUTION: The total amount of either one or two components and more of acrylic acid, methacrylic acid and maleic anhydride of 5W20wt.% is incorporated in styrene-based heat-resistant resin sheet laminated to polystyrene-based resin foamed sheet. Further, said resin sheet is one made by biaxially stretching and has a thickness of 50W250μm. The preferable state of orientation of the sheet is selected from the range of 4W15kg/cm2 in maximum heat shrinkage stress. By heating from both the surface sides of a laminate and selecting the temperature difference from the range of 5W30°C, the laminate is formed in the same molding cycle as that of polystyrene resin foamed sheet.