  We investigate the pressure effect of the electrical resistivity and
magnetization of Ce$_{0.8}$La$_{0.2}$B$_{6}$. The situation in which phase IV
stably exists inside phase II at H=0 T could be realized by applying a pressure
above $P\sim 1.1$ GPa. This originates from the fact that the stability of
phase II under pressure is larger than those of phases IV and III. The results
seem to be difficult to reproduce by taking the four interactions of
$\Gamma_{\mathrm{5u}}$-type AFO, $O_{xy}$-type AFQ, $T_{xyz}$-type AFO, and AF
exchange into account within a mean-field calculation framework.
