A device for automatically milking an animal, which device is provided with a milking robot, a computer for controlling the operation of the device, a measuring device for performing measurements on milk obtained from an animal, at least two teat cups, and a common milk line for discharging milk coming from the at least two teat cups, each teat cup being connected via a teat cup line to the common milk line. The device is provided with a milk-determining element for determining the teat cup from which comes the milk present in the common milk line and for emitting a determination signal. The measuring device comprises a common sensor for performing measurements on milk obtained from an animal and for emitting a measurement signal. The common sensor is disposed in the common milk line. The computer is suitable for combining the measurement signal and the determination signal.