  The $\pi NN$ form factor $g_{\pi NN}(q^2)$ is obtained from a quenched
lattice QCD calculation of the pseudoscalar form factor $g_P(q^2)$ of the
proton with pion pole dominance. We find that $g_{\pi NN}(q^2)$ fitted with the
monopole form agrees well with the Goldberger-Treiman relation and is much
preferred over the dipole form. The monopole mass is determined to be $0.75 \pm
0.14 {\rm GeV}$ which shows that $g_{\pi NN}(q^2)$ is rather soft. The
extrapolated $\pi N$ coupling constant $g_{\pi NN} = 12.7 \pm 2.4$ is quite
consistent with the phenomenological values. We also compare $g_{\pi NN}(q^2)$
with the axial form factor $g_A(q^2)$ to check the pion dominance in the
induced pseudoscalar form factor $h_A(q^2)$ vis \`{a} vis chiral Ward identity.
