Driving assistance device

A driving assistance device comprising one or more processors configured to control operation of a host vehicle, wherein

• the one or more processors are configured to perform first following control controlling acceleration and deceleration of the host vehicle so that the host vehicle follows a first preceding vehicle running in front of the host vehicle in the same lane as the host vehicle, and perform second following control prohibiting the first following control while a lane change is being performed and controlling acceleration and deceleration of the host vehicle so that the host vehicle follows a second preceding vehicle running in front of the host vehicle in a destination lane, if the lane change of the host vehicle is started during the first following control,
• the one or more processors are configured to brake the host vehicle when a target deceleration degree determined based on a relative relationship between the host vehicle and the first preceding vehicle becomes equal to or less than a target deceleration degree threshold value, and
• the target deceleration degree threshold value during the lane change is smaller than the target deceleration degree threshold value before the lane change.