Travel Assistance Method and Travel Assistance Device for Vehicle

A vehicle travel assistance method and a travel assistance device for a vehicle include determining whether or not a route-following lane change that is a lane change for traveling along a set travel route can be assisted with autonomous lane change control, and when determining that the route-following lane change cannot be assisted with the autonomous lane change control, notifying a driver that a lane change with the autonomous lane change control cannot be made, and prohibiting the autonomous lane change control from assisting a lane change in a direction opposite to a direction in which the vehicle moves during the route-following lane change.