PURPOSE: To obtain a highly compressible gasket material which is useful under severe, corrosive environment by sintering and melting a three-layer structure comprising an unsintered polytetrafluoroethylene with an empty, rigid collapsible particle being dispersed and bonded thereto.

CONSTITUTION: First and second sheets of an unsintered polytetrafluoroethylene with an internally completely embedded empty, rigid collapsible particle being dispersed and bonded thereto are prepd. A third unsintered sheet pref. having a thickness twice larger than the first and second sheets is formed. The third sheet is then interposed between the first and second sheets to form a three-layer structure which is then sintered at a temp. of the gel point of the polytetrafluoroethylene or above to melt the third layer, thereby preparing a single gasket structure.