Abstract: The invention relates to a method of manufacturing a sandwich panel (10). Such a sandwich panel consists of a foamed core layer (12) and at least one thermoplastic cover layer (14). The sandwich panel is made by in situ foaming. In a first assembling step a core web, comprising at least one sheet of a thermoplastic material (12) containing an amount of a suitable physical blowing agent is positioned between two cover layers (14). The assembly of core web and cover layers is arranged between two press plates. Due to heat and pressure applied in a subsequent foaming step, foaming of the core web and effective bonding thereof to the cover layers is achieved. Subsequently the foamed assembly is allowed to cool down. Remaining physical blowing agent is removed during a subsequent drying step at elevated temperature while the outflow of physical blowing agent via the peripheral edges of the panel (10) is restricted, e.g. by taping (24) or clamping by clamps (16, 20).