  We discuss bound states appearing at the interface between two different
superconductors characterized by different nontrivial topological numbers such
as one-dimensional winding numbers and Chern numbers. The one-dimensional
winding number characterizes d_{xy} and p_x wave superconductors. The Chern
number characterizes chiral-p, chiral-d, and chiral-f wave superconductors. The
interfacial bound state appears at the zero-energy when the topological numbers
of the two superconductors are different from each other. When the two
superconductors are characterized by the Chern numbers n and m, for example,
the number of the zero-energy bound is |n-m| independent of junction parameters
such as the phase difference across the junction and the transmission
probability of interface. We generalize a concept of bulk-boundary
correspondence to the Josephson junctions consisting of two topological
superconductors.
