There is provided a driving assistance device. An imaging unit is configured to acquire an image of another vehicle running behind one vehicle which is equipped with the driving assistance device. A tailgating determining unit is configured to determine whether the another vehicle is tailgating the one vehicle on the basis of the image acquired by the imaging unit. A continuity determining unit is configured to determine whether tailgating determined by the tailgating determining unit has been performed continuously. An information providing unit configured to provide a driver of the one vehicle with information on the another vehicle, if the continuity determining unit determines that the tailgating has been performed continuously.