  GRB 131108A is a bright long Gamma-Ray Burst (GRB) detected by the Large Area
Telescope and the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space
Telescope. Dedicated temporal and spectral analyses reveal three $\gamma$-ray
flares dominating above 100 MeV, which are not directly related to the prompt
emission in the GBM band (10 keV - 10 MeV). The high-energy light curve of GRB
131108A (100 MeV - 10 GeV) shows an unusual evolution: a steep decay, followed
by three flares with an underlying emission, and then a long-lasting decay
phase. The detailed analysis of the $\gamma$-ray flares finds that the three
flares are 6 - 20 times brighter than the underlying emission and are similar
to each other. The fluence of each flare, (1.6 $\sim$ 2.0) $\times$ 10$^{-6}$
erg cm$^{-2}$, is comparable to that of emission during the steep decay phase,
1.7 $\times$ 10$^{-6}$ erg cm$^{-2}$. The total fluence from three $\gamma$-ray
flares is 5.3 $\times$ 10$^{-6}$ erg cm$^{-2}$. The three $\gamma$-ray flares
show properties similar to the usual X-ray flares that are sharp flux
increases, occurring in $\sim$ 50\% of afterglows, in some cases well after the
prompt emission. Also, the temporal and spectral indices during the early steep
decay phase and the decaying phase of each flare show the consistency with a
relation of the curvature effect ($\alpha$ = 2 + $\beta$), which is the first
observational evidence of the high-latitude emission in the GeV energy band.
