A device for exchanging and/or docking functional modules (1, 2), and used for the extracorporeal circulation of bodily fluids, is provided. Each functional module (1, 2) includes at least one conduit (3; 4) comprising an inlet (5; 7) and an outlet (6; 8). The aim of the invention is to exchange the functional modules of an extracorporeal circuit as rapidly as possible, without detaching tubular connections and without having to establish a new connection. The invention is provided with elements (9, 10; 11, 12) for connecting the conduit (3) of a first functional module (1) to the inlet (5) and the outlet (6) of a second functional module (2). The connection is established in such a way that the first functional module (1) is bypassed by means of the second functional module (2) to maintain the flow and the bodily fluid is diverted through the second functional module (2).