  We study the scalar leptoquark effects on the rare semileptonic decays of
$\Lambda_b$ baryon, governed by the quark level transition $b \to s l^+ l^-$.
We estimate the branching ratios, forward-backward asymmetries, lepton
polarization parameters and the lepton flavour non-universality effects in
these decay channels. We find significant deviations from the corresponding
standard model predictions in some of the observables due to leptoquark
effects. We also investigate the lepton flavour violating decays $\Lambda_b \to
\Lambda l_i^- l_j^+$, the branching ratios of which are found to be ${\cal
O}(10^{-10} - 10^{-9})$.
