  UPt${}_{3}$ exhibits a paradoxical behavior in its antiferromagnetism.
Namely, the neutron scattering experiments surely detect the antifferomagnetic
ordering below the transition temperature ${\rm T}_{N}\sim 5K$, while no trace
of the transition is seen in the NMR experiments and in the specific heat at
${\rm T}_{N}$. For resolution of this paradox, we propose the ``SDW state''
which oscillates with a finite frequency larger than those of the NMR and
smaller than those of the neutron scattering. For demonstrating such
possibility we seek the divergent point of susceptibility, and offer a
preliminary calculation of the frequency dependence of ``magnetization''.
