  Effects of Kaluza-Klein excited neutral vector bosons ($Z'$ bosons) in the
gauge-Higgs unification on $e^+e^- \to \bar{q}q, \ell^+\ell^-$ cross sections
are studied, particularly in future $e^+ e^-$ collider experiments with
polarized beams. Significant deviations in the energy and polarization
dependence in $\sigma(\mu^+\mu^-)$, the lepton forward-backward asymmetry,
$R_b(\mu) \equiv \sigma(\bar{b}b)/\sigma(\mu^+\mu^-)$ and the left-right
asymmetry from the standard model are predicted.
