Abstract: A sealing system is formed of gasket attaching portions facing each other, and a metal gasket. Each gasket attaching portion has a hole to be sealed and a flat surface portion around the hole. When the gasket attaching portions are assembled, the holes and flat surface portions face each other. At least one of the gasket attaching portions has a depression around the hole. The metal gasket includes a main portion situated between the flat surface portions of the gasket attaching portions, and an enlarged hollow portion attached to the main portion and facing the depression. When the gasket is tightened between the gasket attaching portions, the enlarged hollow portion is disposed in the depression and compressed thereat to securely and resiliently seal around the holes of the gasket attaching portions.