  Screenings of the quark-gluon plasma in electric and magnetic sectors are
studied on the basis of generalized Polyakov-line correlation functions in
lattice QCD simulations with two flavors of improved Wilson quarks. Using the
Euclidean-time reflection ($\R$) and the charge conjugation ($\Ca$), electric
and magnetic screening masses are extracted in a gauge invariant manner. Long
distance behavior of the standard Polyakov-line correlation in the quark-gluon
plasma is found to be dictated by the magnetic screening. Also, ratio of the
two screening masses agrees with that obtained from the dimensionally-reduced
effective field theory and the ${\cal N}=4$ supersymmetric Yang-Mills theory.
