Abstract: A sealing device for a fluidtight screw connection. When screwing in a screw to be sealed into a fluid-carrying threaded bore of a component, in order to prevent a rectangular sealing ring from extending into a gap between a radial flange of the screw and the component as a result of tangential stress, the sealing device embodies a rectangular sealing ring having a thinner thickness than a countersink into which the sealing ring is inserted. A radial flange of the screw includes a collar that protrudes into the countersink and elastically compresses the rectangular sealing ring so that the sealing ring rests sealingly against a bottom of the countersink and against the collar of the screw.