A connecting device (20) for connecting a connection hose or connection pipe comprises a tubular connecting branch (2), an operating sleeve (28) and a support sleeve (38). The receiving device to which the connecting device (20) can be connected comprises at least one locking element which can be operated by means of at least one operating element mounted on the receiving device. The connecting branch (2) can be connected to the connection hose or the connection pipe and has a locking projection (20) or locking groove which can engage with the locking element of the receiving device. The operating sleeve (28) is used for operating the operating element of the receiving device. The support sleeve (38) is supported on the receiving device and is axially displaceable in relation to the operating sleeve (28) with the prestress of a first spring (44).
