A travel route generation system comprising: a travel road information acquisition device (20, 21, 22) that acquires travel road information on a travel road of a host vehicle; an obstacle information acquisition device (21, 22) that acquires obstacle information on an obstacle on the travel road; and an arithmetic device (ECU 10) configured to generate a target travel route, on which the host vehicle travels, on the travel road on the basis of the travel road information and the obstacle information, wherein the arithmetic device (ECU 10) is configured to: acquire information on at least two peripheral vehicles (3a, 3b), which exist near the host vehicle on a change destination lane, from the obstacle information when the host vehicle changes the lane; set a target space, to which the host vehicle should move, between the at least two peripheral vehicles (3a, 3b) in the change destination lane on the basis of the information on the at least two peripheral vehicles (3a, 3b); and predict a future position of the target space on the basis of a moving speed of said target space and generate the target travel route, on which the host vehicle travels during a lane change, on the basis of the predicted future position; characterized in that the arithmetic device (ECU 10) is further configured to: generate the target travel route, on which the host vehicle travels during the lane change, on the basis of the predicted future position of the target space in the case where a distance to a point, at which the host vehicle should change the lane, is equal to or longer than a specified distance; and predict a change in size of the target space and generate the target travel route, on which the host vehicle travels during the lane change, on the basis of the predicted change in size of the target space in the case where the distance to the point, at which the host vehicle should change the lane, is shorter than the specified distance. a travel road information acquisition device (20, 21, 22) that acquires travel road information on a travel road of a host vehicle; an obstacle information acquisition device (21, 22) that acquires obstacle information on an obstacle on the travel road; and an arithmetic device (ECU 10) configured to generate a target travel route, on which the host vehicle travels, on the travel road on the basis of the travel road information and the obstacle information, wherein the arithmetic device (ECU 10) is configured to: acquire information on at least two peripheral vehicles (3a, 3b), which exist near the host vehicle on a change destination lane, from the obstacle information when the host vehicle changes the lane; set a target space, to which the host vehicle should move, between the at least two peripheral vehicles (3a, 3b) in the change destination lane on the basis of the information on the at least two peripheral vehicles (3a, 3b); and predict a future position of the target space on the basis of a moving speed of said target space and generate the target travel route, on which the host vehicle travels during a lane change, on the basis of the predicted future position; acquire information on at least two peripheral vehicles (3a, 3b), which exist near the host vehicle on a change destination lane, from the obstacle information when the host vehicle changes the lane; set a target space, to which the host vehicle should move, between the at least two peripheral vehicles (3a, 3b) in the change destination lane on the basis of the information on the at least two peripheral vehicles (3a, 3b); and predict a future position of the target space on the basis of a moving speed of said target space and generate the target travel route, on which the host vehicle travels during a lane change, on the basis of the predicted future position; characterized in that the arithmetic device (ECU 10) is further configured to: generate the target travel route, on which the host vehicle travels during the lane change, on the basis of the predicted future position of the target space in the case where a distance to a point, at which the host vehicle should change the lane, is equal to or longer than a specified distance; and predict a change in size of the target space and generate the target travel route, on which the host vehicle travels during the lane change, on the basis of the predicted change in size of the target space in the case where the distance to the point, at which the host vehicle should change the lane, is shorter than the specified distance. generate the target travel route, on which the host vehicle travels during the lane change, on the basis of the predicted future position of the target space in the case where a distance to a point, at which the host vehicle should change the lane, is equal to or longer than a specified distance; and predict a change in size of the target space and generate the target travel route, on which the host vehicle travels during the lane change, on the basis of the predicted change in size of the target space in the case where the distance to the point, at which the host vehicle should change the lane, is shorter than the specified distance.