Travel Assistance Method and Travel Assistance Device

A travel assistance method for performing a lane change of a host vehicle includes: detecting an oncoming vehicle traveling in an opposite lane from which the host vehicle travels when the host vehicle starts the lane change; determining a crossing point between a virtual advancing route and a linear advancing route in which the oncoming vehicle advances linearly, the virtual advancing route being a virtual extension of an advancing route of the host vehicle during a period from start to end of the lane change; executing a lane change using the route and the vehicle speed in a case where a time difference between a first predicted time and a second predicted time is outside a predetermined range; and when within the predetermined range, executing a lane change by changing at least one of the route and the vehicle speed such that the time difference is outside the predetermined range.