Neural networks are used to classify objects automatically by means of Doppler-broadened radar echo signals. The classification device KK contains a neural network (NET, NET2) which has an input layer (IL) of input nodes (IN1, . . . , IN57) for features (M) of the Doppler-broadened radar echo signals, and an output layer (OL) of output nodes (ON1, ON2, ON3) for predetermined classes to which the objects can be allocated. The neural network (NET, NET2) is adapted to the external conditions prevailing at the time of the classification operation. The adaptation takes place either via accessible input nodes (ZN1, ZN2) into which control information (SI) can be entered, and which cause the neural network (NET) to adapt to one or to several external influence factors, or via a selection device (SEL) which, from the parameters (P1, . . . , P4) of several neural networks stored in a memory (MEM), which are trained with training data under respectively different conditions of external influence factors, selects the one most similar to the prevailing conditions.