The device for fixing a dental prosthesis has a base which can be inserted into a jaw bone, an abutment and a shell. The base has a hole with a mouth at its end face, with an internal thread and with an extension and has a conical annular surface enclosing the mouth of the hole. The abutment has a thread part which passes through the shell in the assembled device and is screwed into the internal thread of the base, and an outer part located outside the base and serving for holding a dental prosthesis. In the assembled device, the shell fits into the extension of the hole and rests with a conical outer surface firmly against a conical inner surface of the base. Furthermore, the outer part of the abutment rests with a conical stop surface firmly against the annular surface of the base. In the assembled device, the abutment is connected to the base in a stable manner and covers its end face without leaving gaps.