  Currents of the SL(N) WZWN model are constrained so that the remaining
symmetry is a symmetry of constrained currents as well. Such consistency
enables us to study the Poisson structure of constrained SL(N) WZWN models
properly. We establish the Poisson brackets which satisfy the Jacobi identities
owing to the classical Yang-Baxter equation. The Virasoro algebra is shown by
using them. An SL(N) conformal primary is constructed. It satisfies a quadratic
algebra, which might become an exchange algebra by its quantum deformation.
