An IVT controller determines whether the operation mode of an infinitely variable transmission (IVT) is a power recirculation mode or a CVT direct mode, and selects an inertial torque computing equation corresponding to the operation mode. The inertia torque accompanying a speed change of the IVT is computed using the computing equation. An engine controller adjusts the opening of an electronic control throttle, and adjusts the torque of the engine so that computed inertia torque is eliminated.