A sheet-like gasket formed of a material having a layered internal structure, for suppressing or preventing leakage penetration, and to attain very high sealing properties together with contact-surface leakage reduction. The sheet-like gasket has two base members each including spaced apart high-density faces and having an outer end portion 1A1 and an inner end portion 1B1 of sheet-like base members 1A and 1B which are adjacent in an inner and outer relationship which are partially overlapped. The whole gasket including the overlap portion is formed by pressurization so as to have a substantially uniform thickness. As a result, double high-density layers and are formed in the overlap portion where the base members are bonded.