We have proposed a theory called the resonating Hartree-Bogoliubov (Res HB) theory to describe large quantum fluctuations in a superconducting Fermion system. One needs also to deal with small quantum fluctuations which correspond to those described by the conventional random phase approximation (RPA). We can derive a new approximation called the Res HB RPA from time dependent small fluctuations of the Res HB ground state. The theory can give a unified description of collective excitations arising from large and small quantum fluctuations and their coupling in a superconducting system. For instance it may be applicable to rotational and vibrational excitations in nuclei with resonance of different deformed shapes.