Zero-energy edge states are discussed for a class of particle-hole symmetric Hamiltonians. We show that the existence of zero-energy edge states can be determined from the bulk properties. A ``loop'' in a parameter space is assigned for each one-dimensional bulk Hamiltonian, and its topological properties, combined with the particle-hole symmetry, play an essential role. It provides a unified framework to discuss zero-energy edge modes for several systems such as fully gapped superconductors, two-dimensional d-wave superconductors, and graphite ribbons.