  In the context of gauge-Higgs unification scenario in a 5-dimensional flat
spacetime, we investigate Higgs boson production via gluon fusion and its
diphoton decay mode at the LHC. We show that the signal strength of the Higgs
diphoton decay mode observed at ATLAS and CMS, which is considerably larger
than the Standard Model expectation, can be explained by a simple gauge-Higgs
unification model with color-singlet bulk fermions to which a half-periodic
boundary condition is assigned. The bulk fermions also play a crucial role in
reproducing the observed Higgs boson mass around 125 GeV.
