  We study the Lee-Yang zeros in the canonical approach to search phase
transition points at finite temperature and density in the Nambu-Jona-Lasinio
(NJL) model as an effective model of QCD. The canonical approach is a promising
method to avoid the sign problem in lattice QCD at finite density. We find that
a set of Lee-Yang zeros computed with finite degrees of freedom can be
extrapolated to those with infinite degrees of freedom, providing the correct
phase transition point. We propose the present method as a useful method for
actual lattice simulations for QCD.
