Abstract: A process and an apparatus for forming a gasket directly on a workpiece having a joining surface which has an annular gasket-fixing groove, wherein a mold having a gasket-forming groove which cooperates with the gasket-fixing groove to define a cavity for forming the gasket is clamped to the joining surface of the workpiece, and a material is injected into the cavity through an injection passage which is formed through the mold and which communicates with the gasket-forming groove. The material is cured into the gasket, and the mold is removed from the workpiece. The mold may have two elastic sealing members disposed on inner and outer sides of the gasket-forming groove, respectively, so as to extend along the gasket-forming groove, and provide pressure-tight sealing of the cavity when the body is placed on the workpiece such that the sealing members are held in elastic pressure-tight contact with the joining surface.