  We report the discovery of a gas giant planet orbiting a low-mass host star
in the microlensing event MOA-bin-29 that occurred in 2006. We find five
degenerate solutions with the planet/host-star mass ratio of $q \sim 10^{-2}$.
The Einstein radius crossing time of all models are relatively short ($\sim
4-7$ days), which indicates that the mass of host star is likely low. The
measured lens-source proper motion is $5-9$ ${\rm mas}\ {\rm yr}^{-1}$
depending on the models. Since only finite source effects are detected, we
conduct a Bayesian analysis in order to obtain the posterior probability
distribution of the lens physical properties. As a result, we find the lens
system is likely to be a gas giant orbiting a brown dwarf or a very late
M-dwarf in the Galactic bulge. The probability distributions of the physical
parameters for the five degenerate models are consistent within the range of
error. By combining these probability distributions, we conclude that the lens
system is a gas giant with a mass of $M_{\rm p} = 0.63^{+1.13}_{-0.39}\ M_{\rm
Jup}$ orbiting a brown dwarf with a mass of $M_{\rm h} = 0.06^{+0.11}_{-0.04}\
M_\odot$ at a projected star-planet separation of $r_\perp =
0.53^{+0.89}_{-0.18}\ {\rm au}$. The lens distance is $D_{\rm L} =
6.89^{+1.19}_{-1.19}\ {\rm kpc}$, i.e., likely within the Galactic bulge.
