  We generalize the topological model recently proposed and investigate the
cosmological perturbations of the model. The model has an exact de Sitter
background solution associated with a Becchi-Rouet-Stora(BRS) quartet terms
which are regarded as a Lagrangian density of the topological field theory. The
de Sitter solution can be selected without spontaneously breaking the BRS
symmetry, and be interpreted as a gauge fixing of de Sitter spacetime. The BRS
symmetry is preserved for the perturbations around the de Sitter background
before we solve the constraints of general relativity. We derive action to the
second order of the perturbations and confirm that even after solving the
constraints, we have the BRS symmetry at least for the second order action. We
construct the cosmological perturbation theory involving the BRS sector, and
obtain the two point correlation functions for the curvature perturbation and
the isocurvature perturbations which compose the BRS sector. Our result gives a
new description for de Sitter spacetime and the quantum field theory in de
Sitter spacetime.
