  We study the possibility of measuring parity-violating pion-nucleon coupling
h_{\pi NN}^{(1)} from \pi^+ electroproton production in the threshold region.
We calculate the electron-helicity asymmetry in terms of h_{\pi NN}^{(1)} and
the Z-boson exchange between the electron and proton in leading-order
heavy-baryon chiral perturbation theory. From the result, we demonstrate that
the coupling can be determined to an accuracy of about 2 10^{-7} in an
experiment with incident electron energy 250 MeV, luminosity 10^{38} sec^{-1}
cm^{-2}, and a running time of 10^7 sec.
