  A simple axion model is proposed in the scenario of large extra dimensions
where gravity scale is as low as 1 TeV. To obtain an intermediate-scale decay
constant of the axion, the axion is assumed to live in a sub-spacetime (brane)
of the whole bulk. In this model there appear Kaluza-Klein modes of the axion
which have stronger interaction than those of the graviton. The axion brane
plays a role of absorber of the graviton Kaluza-Klein modes. Because of these
reasons phenomenology and cosmology of the axion become highly non-trivial. We
discuss various cosmological constraints as well as astrophysical ones and show
that the model is viable for certain choices of the dimensionality of the axion
brane. The structure of the model proposed here provides a viable realization
of the fat brane idea to relax otherwise very severe cosmological constraints.
