The vibrating behavior of a vibratory roller was discussed through numerical simulation as a part of the development research of the ground evaluating system in which the ground stiffness can be evaluated in real-time by monitoring the vibrating behavior of a vibratory roller which depends on the ground stiffness in soil compaction. In the simulation, the vibratory roller-ground system was replaced by the second degree of freedom vibrating model and the reason its vibrating behavior changes according to the ground stiffness and its characteristics were discussed in detail by introducing the consideration of the nonlinear vibration and chaos.