  To clarify the relation between chiral symmetry breaking and color
confinement, we investigate the Polyakov loop in terms of the Dirac eigenmodes
in SU(3) lattice QCD. We analyze the low-lying (IR) and UV Dirac-mode
contribution to the Polyakov loop, respectively, using the Dirac-mode expansion
method. In the confined phase, the Polyakov loop $< L_P >$ remains almost zero
and $Z_3$ center symmetry is thus unbroken, even after removing low-lying
Dirac-modes, which are responsible to chiral symmetry breaking. In the confined
phase, the Polyakov loop $< L_P >$ also remains almost zero by UV Dirac-modes
cut. In addition to the confined phase, we analyze the Polyakov loop in the
deconfined phase and its temperature dependence. The behavior of the Polyakov
loop $< L_P >$ is found to be almost unchanged by the cut of low-lying or UV
Dirac-modes in both confined and deconfined phases.
