A fastening device for fastening an outer container (1) of a drainage container comprises a snap lock (12). Said snap lock (12) has a slot/slot pin connection (42, 13). A leaf spring (12) having a projecting nose (12′) is arranged at a lower end of the connection and engages behind a lower edge of the slot (42) or the slot pin (13). The fastening device according to the invention allows the drainage bag to be replaced in a simple and reliable manner. The corresponding drainage container is inexpensive to produce and allows a reliable operation.
