  We calculate axion potential in antiferromagnetic insulators from path
integral. It is derived from effective potential for order parameter of
antiferromagnetic phase in insulators. Static and dynamical axions are defined
consistently from its potential. Consequently antiferromagnetic/paramagnetic
and topological/normal orders are classified. The dynamical axion is predicted
in all phases and its mass turns out to be various value up to eV scale.
