We address the question as to why the ordering of O-xy-type quadrupole mome
nt predominates that of T-xyz octupole moment at no applied field in CeB6,i
n spite of the same coupling constant predicted. In the mean field approxim
ation (MFA), the same results are obtained for the quadrupolar and the octu
polar interactions. If we go beyond the MFA to apply the constant coupling
approximation, it is shown that the ordering of O-xy is stabilized compared
with that of T-xyz, as far as each interaction is treated separately.