  A stability analysis is made for a non-singular pre-big-bang like
cosmological model based on 1-loop corrected string effective action. Its
homogeneous and isotropic solution realizes non-singular transition from de
Sitter universe to Friedmann-like universe, via super inflation phase. We are
interested in whether the non-singular nature of the solution would be stable
or not in more general inhomogeneous case. Perturbative analysis is made for
scalar, vector, and tensor linear perturbations, and instability is found for
tensor-type perturbation.
