A route guidance device used for a vehicle which provides a travel route to a predetermined destination or an autonomous vehicle which is autonomously driven along the travel route, the route guidance device comprising: a position estimation unit configured to estimate a position of a host vehicle, wherein the estimation unit is configured to estimate a travel lane in which the host vehicle is traveling as the position of the host vehicle; a guide unit configured to lead the host vehicle to change lanes toward the travel route; and an accuracy determination unit configured to determine accuracy of the travel lane of the host vehicle estimated by the position estimation unit, wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is greater than a predetermined threshold, the guide unit leads the host vehicle to change lanes toward the travel route when a distance from the position of the host vehicle estimated by the position estimation unit to a branch point on the travel route reaches a predetermined distance; characterized in that wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is the predetermined threshold or less, the guide unit leads the host vehicle to change lanes toward the travel route at a point before the distance from the position of the host vehicle to the branch point reaches the predetermined distance, wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is the predetermined threshold or less and the branch point is on right direction, the guide unit leads the host vehicle to change the travel lane to a rightmost lane, and wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is the predetermined threshold or less and the branch point is on left direction, the guide unit leads the host vehicle to change the travel lane to a leftmost lane. a position estimation unit configured to estimate a position of a host vehicle, wherein the estimation unit is configured to estimate a travel lane in which the host vehicle is traveling as the position of the host vehicle; a guide unit configured to lead the host vehicle to change lanes toward the travel route; and an accuracy determination unit configured to determine accuracy of the travel lane of the host vehicle estimated by the position estimation unit, wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is greater than a predetermined threshold, the guide unit leads the host vehicle to change lanes toward the travel route when a distance from the position of the host vehicle estimated by the position estimation unit to a branch point on the travel route reaches a predetermined distance; characterized in that wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is the predetermined threshold or less, the guide unit leads the host vehicle to change lanes toward the travel route at a point before the distance from the position of the host vehicle to the branch point reaches the predetermined distance, wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is the predetermined threshold or less and the branch point is on right direction, the guide unit leads the host vehicle to change the travel lane to a rightmost lane, and wherein, when the accuracy determination unit determines that the accuracy of the travel lane of the host vehicle is the predetermined threshold or less and the branch point is on left direction, the guide unit leads the host vehicle to change the travel lane to a leftmost lane.