In this study, the effect of the level of ESG activity of companies, which is receiving worldwide attention, on stock price informativeness, is to be confirmed through empirical analysis. Specifically, in this study, the effect of ESG activity on stock price informativeness was empirically analyzed through stock price synchronicity to determine how the ESG activity performance of an individual company had an effect on the volatility of market returns and industrial returns. If investors judge a company’s ESG activities and performance as useful accounting information for forecasting future prospects, they will make investment decisions with more weight on the company’s ESG information when forming future earnings expectations. In this case, the level of stock price movement will be low due to the high explanation of the company’s ESG information. On the other hand, ESG activities and performance will facilitate the use of future vision and information for investors, which will improve the flow of information to the market, and increase information efficiency, which will improve stock price information. The research sample was December settlement companies in the KOSPI market and KOSDAQ market from 2018 to 2021, targeting non-financial listed corporations, and ESG, the main independent variable, was subjected to empirical analysis targeting KOSPI 200 ESG constituents. As a result of empirical analysis, a company’s ESG activity showed a significant positive(+) correlation with stock price movement. This shows that ESG-active companies have high information efficiency because the unique information of individual companies is sufficiently reflected in the stock price. In other words, it can be judged that companies that actively engage in ESG activities have a high level of information environment and that sufficient information is reflected in their stock prices. The implication of this study is that it will be helpful for creditors and investors to make investment decisions by considering ESG management activities and performance information of companies as ethical management and transparency based on the results of this study. And it is expected that it will be able to induce ESG management activities of companies.