  General neutrino-scalar couplings appear in many extensions of Standard
Model. We can probe these neutrino-scalar couplings by leptonic decay of mesons
and from heavy neutrino search. Our analysis improves the present limits to
$|g_e|^2<1.9\times 10^{-6}$ and $|g_\mu|^2<1.9\times 10^{-7}$ at 90\% C.L. for
massless scalars. For massive scalars we found for the first time the
constraints for $g^2_{\alpha}$ couplings to be $10^{-6}-10^{-1}$ respectively
for scalar masses between below 1 MeV and for 300 MeV.
