A travel assistance method for performing a lane change of a host vehicle using a determined route and vehicle speed, the travel assistance method comprising: detecting an oncoming vehicle traveling in an opposite lane opposite to a lane in which the host vehicle travels when the host vehicle starts the lane change; characterised in that it further comprises: 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 differing from the route and being a virtual extension of an advancing route of the host vehicle in an advancing direction 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 (ta) when it is assumed that the host vehicle reaches the crossing point and a second predicted time (tb) until the oncoming vehicle reaches the crossing point is outside a predetermined range; and when the time difference is 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. detecting an oncoming vehicle traveling in an opposite lane opposite to a lane in which the host vehicle travels when the host vehicle starts the lane change; characterised in that it further comprises: 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 differing from the route and being a virtual extension of an advancing route of the host vehicle in an advancing direction 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 (ta) when it is assumed that the host vehicle reaches the crossing point and a second predicted time (tb) until the oncoming vehicle reaches the crossing point is outside a predetermined range; and when the time difference is 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. 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 differing from the route and being a virtual extension of an advancing route of the host vehicle in an advancing direction 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 (ta) when it is assumed that the host vehicle reaches the crossing point and a second predicted time (tb) until the oncoming vehicle reaches the crossing point is outside a predetermined range; and when the time difference is 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.