An extracorporeal blood treatment device is provided that includes a hydraulic system having a plurality of flow paths. A control unit provides an operating mode for disinfecting the hydraulic system with a liquid supplied via one of the flow paths. A method for operating the extracorporeal blood treatment device is also provided. The hydraulic system has a valve device that provides several switching positions. The valve device has an inlet for a liquid for disinfecting the hydraulic system, and a plurality of outlets. In a first switching position, the inlet is connected to one of the outlets. In another switching position, the inlet is connected to a plurality of the outlets. The inlet of the valve device is in fluid communication with a first flow path and the outlets are in fluid communication with another flow path. Disinfecting liquid can simultaneously be supplied to the individual flow paths.