  The seesaw-induced neutrino mass is discussed in a generic class of curved
spacetime, including the flat and warped extra dimensions. For Majorana masses
in the bulk and on the boundary, the exact forms of seesaw-induced masses are
derived by using the Kaluza-Klein mode expansion and the lepton number
violating correlator for bulk fermion. It is found that the neutrino mass is
determined without the knowledge of wave functions and whole background
geometry when the metric factor is fixed on the boundary, e.g. by solving the
hierarchy problem.
