In this paper, an element of vibration control system is discussed, that is inertial mass between ordinary mass points and has kinetic energy proportional to the square of the relative velocity between the mass points. Utilizing this element for response control of multi-degree system against earthquake, natural period of structure can be changed without changing its eigen vectors. Participation vectors of higher modes can be made 0. Especially, the combination of this element can be evaluated easily, that makes all participation vectors of higher modes except the 1st mode 0. In this way, a structure can be realized, that dose not have response of higher modes, and whose response shear coefficients of all stories are the same.
