  Responses to chemical potential of the pseudoscalar meson screening mass and
the chiral condensate in lattice QCD are investigated. On a $16 \times 8^2
\times \4$ lattice with two flavors of staggered quarks the first and second
responses below and above $T_c$ are evaluated. Different behavior in the low
and the high temperature phases are observed, which may be explained as a
consequence of the chiral symmetry breaking and restoration.
