  In light of a discrepancy of the direct $CP$ violation in $K\to\pi\pi$
decays, $\varepsilon'/\varepsilon_K$, we investigate gluino contributions to
the electroweak penguin, where flavor violations are induced by squark
trilinear couplings. Top-Yukawa contributions to $\Delta S = 2$ observables are
taken into account, and vacuum stability conditions are evaluated in detail. It
is found that this scenario can explain the discrepancy of
$\varepsilon'/\varepsilon_K$ for the squark mass smaller than 5.6 TeV. We also
show that the gluino contributions can amplify $\mathcal{B}(K \to \pi \nu
\overline{\nu})$, $\mathcal{B}(K_S \to \mu^+ \mu^-)_{\rm eff}$ and $\Delta
A_{\rm CP}(b\to s\gamma)$. Such large effects could be measured in future
experiments.
