A foamed laminate sheet suitable for thermoforming and a double-side vacuum forming process using the same are disclosed, said foamed laminate sheet being composed of a foamed interlayer comprising a polyolefin resin as a main resinous component and from 0.5 to 35 parts by weight of an inorganic filler per 100 parts by weight of the polyolefin resin, said foamed interlayer having a density of from 0.18 to 0.98 g/cm.sup.3, and a polyolefin film laminated on both sides of said foamed interlayer. The foamed laminate sheet exhibits excellent formability, and formings obtained therefrom have excellent heat resistance, oil resistance, heat insulating properties, and strength, with outstanding use in a microwave oven or as a retort food container.