A cooling device (10) for a functional system, in particular a fuel cell system (12) for a motor vehicle is disclosed. The cooling device (10) includes a conduit system (14, 22) for a cooling fluid flow connected to the functional system (12) for cooling. A container (20) of the cooling device (10) for the cooling fluid is fluidically connected to the conduit system (14, 22). A treatment unit, in particular an ion exchanger (24), for treating the cooling fluid is fluidically connected to the conduit system (14, 22). The container (20) includes a receptacle chamber to receive the treatment unit (24) and/or an ion exchanger (24) disposed so as to stand upright in the container (20).