This paper will show a design method of active vibration isolation control for a benchmark problem of a tall building subjected to seismic disturbances. The reduced-order model will be derived by applying the balanced realization method and the robust controller for the model will be obtained by the m-synthesis approach. We have already shown that suppression of the interaction between the controlled structure and the base was effective for an active vibration isolation of a multi-degree-of-freedom of which the base was subjected to an input such as a seismic excitation. This design strategy will be applied to the determination of the controlled values for the real tall building. Although the control objectives by the controller designed for the reduced-order model is to suppress the vibration of the frequency range of the model and to hold the stability of the higher modes than the model, the purpose of the proposed controller design is to isolate the all modes including not only the controlled modes but also the truncated modes. By simulations it will be verified that the controller designed for the reduced-order model can isolate not only the reduced-order modes but also the vibration in the higher frequency range than that of the reduced-order model and have appropriate robust performance for the parameter variations of the seismically excited building. Comparison of the control performances between by the proposed vibration isolator and by an active mass damper will be performed.