  The form factors and the coupling constant of the $B_s^* B K$ vertex are
calculated using the QCD sum rules method. Three point correlation functions
are computed considering both $K$ and $B$ mesons off-shell and, after an
extrapolation of the QCDSR results, we obtain the coupling constant of the
vertex. We study the uncertainties in our result by calculating a third form
factor obtained when the $B^*_s$ is the off-shell meson, considering other
acceptable structures and computing the variations of the sum rules'
parameters. The form factors obtained have different behaviors but their
simultaneous extrapolations reach to the same value of the coupling constant
$g_{B_s^* B K}=10.6 \pm 1.7$. We compare our result with other theoretical
estimates.
