A trajectory tracking control unit carries out a trajectory tracking control in the event that a predetermined condition is satisfied. On the other hand, in the case that a preceding vehicle recognizing unit detects that a preceding vehicle has moved in a vehicle transverse direction, the trajectory tracking control unit predicts that the preceding vehicle will depart from a lane in which it is traveling. Therefore, even if the predetermined condition is satisfied after the preceding vehicle recognizing unit has detected that the preceding vehicle has moved in the vehicle transverse direction, the trajectory tracking control unit does not cause the driver's own vehicle to follow the trajectory of the preceding vehicle.