If the dynamics of combined vehicle varies large, it may be very difficult for inexperienced drivers to achieve good handling stability. Once combined vehicles become unstable, it is very difficult for all of drivers to stabilize vehicles. However, if the behavior of actual combined vehicle tracks a designed combined vehicle, the good handling property can be maintained even when the dynamics of actual combined vehicle varies large. In the paper, to achieve good handling property even for large variation of vehicle dynamics, a design method of a desired combined vehicle is proposed. Then, an adaptive steering controller is developed so that the actual vehicle tracks the desired vehicle.