Online game industry is an emerging entertainment software industry as a successful and fast growing one, but while it reveals many characteristics distinctive from traditional ones such as movies, to the best of our knowledge, studies capturing them are still very sparse. One of key business challenge this industry faces is securing investment for development since it requires relatively huge investment during the production and initial marketing stage. We analyze relationship between events that would be announced in the development process such as game rating information, public announcements about public beta tests, and stock market price in the online game industry and identify what kinds of process have impacts on the market. We examine the information of 9 online game companies from 2002 to 2009 that are listed in Korean stock markets. In this study we adopt event study methodology, widely used in finance and MIS literature. Our results show strong positive correlation between the game rating events and stock price reaction. Finally we suggest implications for policy makers and firm managers to improve value of the online game industries.