The invention relates to a device for extracorporeal blood treatment, having a hydraulic system B which comprises multiple lines (7), (9) for providing dialysate for a dialyser (3) and having a control system (15) which comprises multiple electrical components (17A), (17B), (17C). The invention also relates to a method for operating a device for extracorporeal blood treatment which has a hydraulic system which comprises multiple lines for providing dialysate for a dialyser and a control system which comprises multiple electrical components, wherein the dialysate is produced using a liquid supplied to the device for extracorporeal blood treatment. The extracorporeal blood treatment device is a blood treatment device which has a central connection (11) to allow a liquid, in particular permeate (pure water), to be supplied to the machine. The blood treatment device is characterised by a cooling apparatus (19) for cooling at least one of the electrical components (17A), (17B), (17C) of the control system (15), said cooling apparatus using the liquid, in particular permeate (pure water), supplied centrally to the device to dissipate heat from the electrical components. The cooling apparatus (19) has at least one heat sink (21) which can be cooled with a liquid and is in thermal contact with the at least one electrical component (17A), (17B), (17C), wherein the cooling apparatus (19) has at least one inlet (22A) which is fluid-connected to the connection (11) for the inflow of a liquid and at least one outlet (22B) which is fluid-connected to a drain (10), (31).
