  In this paper, we investigate the finiteness of the Higgs effective potential
in an ${\rm SU}(\mathcal N)$ Gauge-Higgs Unification (GHU) model defined on
${\bf M}^4\times S^1$. We obtain the Higgs effective potential at the two-loop
level and find that it is finite. We also discuss that the Higgs effective
potential is generically divergent for three- or higher-loop levels. As an
example, we consider an ${\rm SU}(\mathcal N)$ gauge theory on ${\bf M}^5\times
S^1$, where the one-loop corrections to the four-Fermi operators are divergent.
We find that the Higgs effective potential depends on their counter terms at
the three-loop level.
