Driving assistance device and driving assistance method

A driving assistance method of a driving assistance device including an external environment detection sensor of a vehicle, and a controller configured to control a drive source of the vehicle,

• the method comprising:
• controlling the drive source so as to change acceleration of the vehicle on the basis of relative information including at least any one of an arrival time, a distance, or a relative speed with respect to a predetermined position ahead or another vehicle ahead in a self-vehicle traveling lane in which the vehicle travels, and a traveling status in another traveling lane as a merging destination on the basis of information of the external environment detection sensor performed by the controller.