A filter device has a filter housing having two separable housing parts (1 and 11) that can receive at least one filter element (21). The housing parts can be connected to one another by a coupling device (7). The filter element (21), or an adapter that can be connected to it, forms a functionally essential component of the coupling device (7). Only when the filter element (21) has been placed in its functional position within at least one of the housing parts (1, 11), can the housing parts (1, 11) be connected to form the filter housing of a functional filter device.