  We consider the Parity Nonconserving (PNC) mixing in the ground state of
exotic (halo) nuclei caused by the PNC weak interaction between outer neutron
and nucleons within nuclear interior. For the nucleus $^{11}Be$ as an example
of typical nucleus with neutron halo, we use analytical model for the external
neutron wave functions to estimate the scale of the PNC mixing. The amplitude
of the PNC mixing in halo state is found to be an order of magnitude bigger
than that of typical PNC mixing between the ``normal'' nuclear states in nearby
nuclei. The enhanced PNC mixing in halo cloud is proportional to the neutron
weak PNC potential constant $g^W_n$ only.
