In a power steering device comprising a power steering pump, and to a method for operating a power steering device for a vehicle comprising a hydraulic circuit provided with a rotary slide valve, a steering cylinder and a control valve for adjusting the volume flow of a hydraulic medium as required for steering assistance, the control valve is arranged on the pressure side of the pump in such a way that it divides the volume flow (Q) from the power steering pump into at least a first base partial flow (A) and a second controlled partial flow (B), the base partial flow (A) being independent from the operating state of the control valve and always available for steering assistance, whereas the partial flow (B) is dependent on the operating state of the control valve.