  Once the quark chemical potential $\mu$ is introduced in finite density QCD,
the fermion determinant appeared in the path integral measure becomes complex.
In order to investigate the phase effect of SU(3) lattice QCD (2-flavors), we
calculated the fluctuation of the phase of $\det\Delta(\mu)$ on a $8^3\times4$
lattice at $\mu = 0.1$ and 0.2. Then we calculated the chiral condensate and
Polyakov line in the no phase and reweighted cases. There is little difference
between these two cases at $\mu = 0.1$ and 0.2. We consider a possible reason
for this result below $\mu \le 0.27$ in terms of $Z_3$ symmetry.
