This is a research on naturalism of Syun-tzu(荀子) through himself evil-nature(性惡)concept. Syun-tzu, lived in Warring-States period, advocated men was center of the world. Then humanity, not nature way, was the standard of human behaviors and society development. However, the innate evil-nature of men cut off the way seeking to righteousness through self instincts like Confucius or Mencius(孔孟). But just because of the factor above, Syun-tzu put the righteousness acquirement through extrinsic knowledge world. The righteousness of men rested on accordance with the objective circulation world. Men must judged good behaviors to make himself a saint through knowledge got from outside world. That is the so-called ”naturalism” discussed in this article.