Disclosed is a method of manufacturing a flexible laminate substrate having an improved appearance and dimensional stability after removal of a metal foil. Specifically disclosed is a method of manufacturing a flexible laminate substrate 5 wherein a metal foil 2 is bonded to at least one surface of a heat-resistant adhesive film 3. The method comprises a step wherein the heat-resistant adhesive film 3 and the metal foil 2 are thermally laminated between a pair of metal rolls 4 via a protective film 1, thereby forming a laminate 7 wherein the heat-resistant adhesive film 3, the metal foil 2, and the protective film 1 are bonded together, and another step wherein the protective film 1 is removed. The tension of the laminate 7 at the time when the protective film 1 is removed is higher than the tension of the laminate 7 before the removal of the protective film 1.