  We study the meson-meson and meson-baryon interactions in lattice QCD. The
simulation is performed on 20^3 * 24 lattice at \beta=5.7 using Wilson gauge
action and Wilson fermion at the quenched level. By adopting one static quark
for each hadron as "heavy-light meson" and "heavy-light-light baryon", we
define the distance $r$ of two hadrons and extract the inter-hadron potential
from the energy difference of the two-particle state and its asymptotic state.
We find that both of the meson-meson and meson-baryon potentials are
nontrivially weak for the whole range of 0.2 fm <= r <= 0.8 fm. The effect of
including/excluding the quark-exchange diagrams is found to be marginal.
