We studied the critical endpoint of 4-flavor QCD at finite temperature and zero chemical potential. Our lattice QCD simulations have been performed with the Iwasaki gauge and the non-perturbatively $O(a)$-improved Wilson fermion actions on lattices with $N_t$ = 4, 6 and 8. We determined the critical endpoint from an intersection point of kurtosis of the chiral condensate with three different volumes for each $N_t$. In this talk we show our preliminary results on a location of the critical endpoint in the continuum limit.

Nonzero Temperature and Density