A medical connector, of a female luer type, comprises an external tubular body (4) which contains an internal tubular body (2) free to rotate about an axis thereof. The external tubular body exhibits a screw-coupling surface. The internal tubular body exhibits a conical luer seal surface. An insert (5), which has a pawl (9) snap-fitted in a window (8) afforded on the external tubular body, constrains the two tubular bodies solidly to one another, in an axial displacement direction. The connector is used to connect a blood line to a blood port of a dialyser, preventing the blood line from twisting on itself and kinking.