To sustain the competitive edges in the online game industry, many publishers invest online game developers at early stages. However, the fair value of online game developers at early stages cannot be calculated with traditional valuation methods due to the high level of uncertainties in technology and market. Based on the literature reviews, we recommended real options analysis for the proper valuation methods of online game developers at early stages, and compared it with other methods using "Bluehole Studio" investment case. The case study result showed that real options analysis is better in explaining the market value as expected.