Abstract: A resin composition which exhibits good sealability while keeping creep deformation to a minimum when brought into sliding contact with a mating member at a high contact pressure of over 10 MPa, and which will not damage a mating member made from an aluminum alloy while sliding in contact with lubricating oil. The resin composition is a pressure-resistant, sliding tetrafluoroethylene resin composition containing 100 parts by volume of a modified tetrafluoroethylene resin in the form of a copolymer of tetrafluoroethylene and partially modified tetrafluoroethylene, 5-40 parts by volume of carbon fiber, and 2-30 parts by volume of calcium sulfate whiskers having a Mohs hardness of 4 or less, and having, at 100° C., a maximum deformation rate in 24 hours, of 15% or less. A seal device to be brought into slide contact with an aluminum metal is molded from such a pressure-resistant, sliding tetrafluoroethylene resin composition.