  We discuss CP violation in the five dimensional $SU(3) \otimes SU(3)_{\rm
color}$ gauge-Higgs unification scenario in which the fifth dimension is
compactified on an orbifold $S^1 /Z_2$. It is shown that CP-violating phase
appears even in the two generation case in contrast with the fact that at least
three generations are required to break CP symmetry in the Standard Model. As
our prediction, we obtain the phenomenological constraint on the
compactification scale by comparing the typical CP-violating observables,
namely $\varepsilon_K$ parameter and the mass difference of two neutral $K$
mesons $\Delta m_K$ with experimental data.
