We consider the motion of the N -vortex points that are equally spaced along a line of latitude on sphere with fixed pole vortices, called "N -ring". We are especially interested in the case when the number of the vortex points is odd. Since the eigenvalues that determine the stability of the odd Nring are double, each of the unstable and stable manifolds corresponding to them is two-dimensional. Hence, it is generally difficult to describe the global structure of the manifolds. In this article, based on the linear stability analysis, we propose a projection method to observe the structure of the iso-surface of the Hamiltonian, in which the orbit of the vortex points evolves. Applying the projection method to the motion of the 3-ring and 5-ring, we characterize the complex evolution of the unstable odd N -ring from the topological structure of the iso-surface of the Hamiltonian.