  On an assumption that the HO is the antiferro-quadrupolar order with
\Gamma_{5} (Q_{z(x+y)} and Q_{z(x-y)}) symmetry, the anisotropy in temperature
dependence of resistivity (\rho_{c}\propto T^{2}, and \rho_{ab}\propto T) in
the HO phase of URu_2Si_2 is explained.
