  The complex scaling method (CSM) is one of the most powerful methods of
describing the resonances with complex energy eigenstates, based on
non-Hermitian quantum mechanics. We present the basic application of CSM to the
properties of the unbound phenomena of light nuclei. In particular, we focus on
many-body resonant and non-resonant continuum states observed in unstable
nuclei. We also investigate the continuum level density (CLD) in the scattering
problem in terms of the Green's function with CSM. We discuss the explicit
effects of resonant and non-resonant contributions in CLD and transition
strength functions.
