  Baryon number is an accidental symmetry in the standard model, while
Peccei-Quinn symmetry is hypothetical symmetry which is introduced to solve the
strong CP problem. We study the possible connections between Peccei-Quinn
symmetry and baryon number symmetry. In this framework, an axion is identified
as the Nambu-Goldstone boson of baryon number violation. As a result,
characteristic baryon number violating processes are predicted. We developed
the general method to determine the baryon number and lepton number of new
scalar in the axion model.
