  In order to understand magnetic behavior observed in CmO$_2$ with
non-magnetic ground state, we numerically evaluate magnetic susceptibility on
the basis of a seven-orbital Anderson model with spin-orbit coupling. Naively
we do not expect magnetic behavior in CmO$_2$, since Cm is considered to be
tetravalent ion with six $5f$ electrons and the ground state is characterized
by $J$=0, where $J$ is total angular momentum. However, there exists magnetic
excited state and the excitation energy is smaller than the value of the
Land\'e interval rule due to the effect of crystalline electric field
potential. Then, we open a way to explain magnetic behavior in CmO$_2$.
