  We discuss flavor mixing and resulting Flavor Changing Neutral Current (FCNC)
in a five dimensional SU(3)_color \otimes SU(3) \otimes U'(1) gauge-Higgs
unification. Flavor mixing is realized by the fact that the bulk and brane
localized mass terms are not diagonalized simultaneously. As the concrete FCNC
processes, we calculate the rate of B^0_d-\bar B^0_d mixing and B^0_s-\bar
B^0_s mixing due to the exchange of non-zero Kaluza-Klein gluons at the tree
level. We obtain a lower bound on the compactification scale of order O(TeV) by
comparing our prediction on the mass difference of neutral B meson with the
recent experimental data.
