A driver assistance device according to an embodiment includes a coupling angle acquirer that acquires a coupling angle between a towing vehicle and a towed vehicle coupled to the towing vehicle; and a notifier that issues a given notification in the towing vehicle when the towing vehicle is driven with the towing vehicle and the towed vehicle differing in orientation at a given value or more based on the coupling angle, the towing vehicle moves in a given distance or less while maintaining a steering angle, and the steering angle of the towing vehicle enables the towing vehicle and the towed vehicle to be placed in a serial state with the towing vehicle and the towed vehicle substantially matching with each other in orientation.