Driving assistance method and driving assistance device

A driving assistance method for causing a controller to perform processing of making a proposal of a lane change to a passenger when an index value based on relative speed of a preceding vehicle with respect to an own vehicle is less than a threshold value and canceling the proposal of the lane change when a lane change execution condition depending on a travel environment of the own vehicle is not satisfied, wherein the controller performs processing including:

• accepting setting of the threshold value;
• and
• not presenting a lane change proposal after the proposal of the lane change is canceled depending on the travel environment until a set time elapses from a time point when the proposal of the lane change is canceled, even when the index value is less than the threshold value, and
• the set time is set to a longer time when the threshold value is high than when the threshold value is low.