A travel assistance method causes a sensor to detect a lane boundary present around a vehicle, calculates own positions of the vehicle, converts a coordinate system of the detected lane boundary into a coordinate system equivalent to map data stored in in accordance with the own positions, and integrates configuration information on the lane boundary included in the map data with the lane boundary of which the coordinate system is converted to generate integrated data, wherein an integrated range is determined, when the configuration information is integrated with the lane boundary of which the coordinate system is converted, such that the lane boundary includes at least either parts having different curvatures or straight parts directed in different directions, and the configuration information is mapped with the lane boundary of which the coordinate system is converted to generate the integrated data while including at least the determined integrated range.