A connecting device is made available for connecting the distal part of a penis to a penis extension device, wherein the connecting device (1) has an elongate, rigid hollow body (3), which is open at the proximal end and is used for receiving the distal end of the penis and for securing on the penis extension device and, at its distal end, has an opening (31) that is in operational connection to a vacuum pump (4) or can be brought into such an operational connection, and an elastic tubular sleeve (2) which is placed with its proximal area (5) onto the shaft of the penis and which, when the connecting device (1) is in the assembled state, has its distal area (6) enclosing the proximal end of the hollow body (3) and bearing on the outside thereof. This connecting device is characterized in that the wall thickness of the sleeve (2) in the distal area (6) is greater than in the proximal area (5) and/or a three-way valve is arranged between the opening (31) and the vacuum pump (4) and can assume the following positions: i) the interior of the hollow body (3) is connected to the environment, ii) the opening (31) and therefore the hollow body (3) are closed, and iii) the interior of the hollow body (3) is connected to the vacuum pump (4).
