A driving assistance device communicates with an information processing device for providing driving assistance. The driving assistance device includes: an electronic control unit configured to: acquire signal information from the information processing device, the signal information indicating a time at which a traffic light on a traveling route displays a stop indication, the traveling route being a route on which a vehicle is traveling; make a prediction whether the vehicle should stop at the traffic light, based on a traveling state of the vehicle and the signal information; and perform the driving assistance and control an operation of the vehicle around the traffic light based on the prediction.