  Effects of the $\Sigma$N channels on the spin-orbit force in
$\Lambda$-hypernuclei are investigated. It is found that the cancellation
between the symmetric and the antisymmetric $\Lambda$N spin-orbit force becomes
more complete when the contribution from the $\Sigma$N channels is included.
This may be the one of the reasons why the observed LS splitting of the
$\Lambda$ single particle energy is very small.
