  The $W$ boson mass $m_W$ in the GUT inspired $SO(5) \times U(1) \times SU(3)$
gauge-Higgs unification in the Randall-Sundrum (RS) warped space is evaluated.
The muon decay $\mu^- \rightarrow e^- \bar{\nu}_e \nu_\mu$ proceeds by the
exchange of not only the zero mode of the $W$ boson $(W^{(0)}$) but also
Kaluza-Klein (KK) excited modes $W^{(n)}$ and $W_R^{(n)}$ ($n \ge 1$) at the
tree level. The anti-de Sitter curvature of the RS space also affects the
relationship among the gauge couplings and the ratio of $m_W$ to the $Z$ boson
mass $m_Z$. The $W$ couplings of leptons and quarks also change. With the given
KK mass scale $m_{\rm KK}$ the range of the Aharonov-Bohm phase $\theta_H$ in
the fifth dimension is constrained. For $m_{\rm KK} = 13\,$TeV, $0.085 \lesssim
\theta_H \lesssim 0.11$ and $80.381\,{\rm GeV} \lesssim m_W \lesssim
80.407\,{\rm GeV}$. The predicted value of $m_W$ for $13\, {\rm TeV} \le m_{\rm
KK} \le 20\, {\rm TeV}$ lies between $m_W^{\rm SM} = 80.354 \pm 0.007\,$GeV in
the standard model and $m_W^{\rm CDF} = 80.4335 \pm 0.0094\,$GeV, the value
reported by the CDF collaboration in 2022.
