A travel route generation system comprising: a travel road information acquisition device (21, 22, 30) 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 to 3e), 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 (SP1, SP2, SP3), to which the host vehicle should move, between the at least two peripheral vehicles (3a to 3e) in the change destination lane on the basis of the information on the at least two peripheral vehicles (3a to 3e); predict a change in size of the target space (SP1, SP2, SP3); and generate the target travel route, on which the host vehicle travels during a lane change, on the basis of the predicted change in the size of the target space (SP1, SP2, SP3); characterized in that the arithmetic device (ECU 10) is further configured to: set a target point (P1, P2, P3) at a center of the target space (SP1, SP2, SP3), wherein the target point (P1, P2, P3) serves as a travel mediating point that is used when the target travel route for the lane change is set, and generate such a target travel route that the host vehicle starts changing the lane when the relative speed between the speed of the host vehicle and the moving speed of the target point becomes lower than a specified speed. a travel road information acquisition device (21, 22, 30) 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 to 3e), 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 (SP1, SP2, SP3), to which the host vehicle should move, between the at least two peripheral vehicles (3a to 3e) in the change destination lane on the basis of the information on the at least two peripheral vehicles (3a to 3e); predict a change in size of the target space (SP1, SP2, SP3); and generate the target travel route, on which the host vehicle travels during a lane change, on the basis of the predicted change in the size of the target space (SP1, SP2, SP3); acquire information on at least two peripheral vehicles (3a to 3e), 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 (SP1, SP2, SP3), to which the host vehicle should move, between the at least two peripheral vehicles (3a to 3e) in the change destination lane on the basis of the information on the at least two peripheral vehicles (3a to 3e); predict a change in size of the target space (SP1, SP2, SP3); and generate the target travel route, on which the host vehicle travels during a lane change, on the basis of the predicted change in the size of the target space (SP1, SP2, SP3); characterized in that the arithmetic device (ECU 10) is further configured to: set a target point (P1, P2, P3) at a center of the target space (SP1, SP2, SP3), wherein the target point (P1, P2, P3) serves as a travel mediating point that is used when the target travel route for the lane change is set, and generate such a target travel route that the host vehicle starts changing the lane when the relative speed between the speed of the host vehicle and the moving speed of the target point becomes lower than a specified speed. set a target point (P1, P2, P3) at a center of the target space (SP1, SP2, SP3), wherein the target point (P1, P2, P3) serves as a travel mediating point that is used when the target travel route for the lane change is set, and generate such a target travel route that the host vehicle starts changing the lane when the relative speed between the speed of the host vehicle and the moving speed of the target point becomes lower than a specified speed.