Motivated by the scenario of electroweak baryogenesis in the walking technicolor (WTC) model, we investigate thermodynamic properties of 8-flavor QCD by using Monte Carlo simulations in the lattice gauge theory framework. We adopt HISQ and tree-level Symanzik improved actions. We show that the chiral susceptibility has a peak structure, and that the ratio of chiral to pion susceptibilities starts showing an inflection point with decreasing fermion mass. These results suggest the existence of a chiral phase transition in 8-flavor QCD.