  The phase structure of Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model
is explored at imaginary chemical potential, with particular emphasis on the
deconfinement transition. We point out that the statistical confinement nature
of the model naturally leads to characteristic dependence of the chiral
condensate $<\bar{q}q>$ on $\theta=\mu_I/T$. We introduce a dual parameter for
the deconfinement transition by making use of this dependence. By changing a
four-fermion coupling constant, we tune the location of the critical endpoint
of the deconfinement transition.
