  We propose a new method, using the Andreev reflection at superconductors, to
measure parity violation induced by the standard electroweak theory, which in
turn constrains the possible parity-violating effects of new physics. The weak
neutral currents induce parity-violating, marginal effective operators, though
quite tiny, in superconductors. We estimate their effects on superconducting
gaps and propose a method to measure the parity-violation from the spin
polarization effect, when electrons or holes get Andreev-reflected at the
interface between normal metal and a superconductor. Such polarization effects
might be comparable to the atomic parity violation and thus naturally give an
interesting bound on certain models of new physics, that couples to electrons,
such as Majorana mass of active neutrinos or doubly charged Higgs.
