Under traditional analysis of the capital budgeting, it is assume that management cannot react to deviation from the expected scenario of cash flows. In practice, however, it is less likely that the expected scenario will come true when new information arrives and uncertainty is resolved. Uncertainty and risk can be influenced through ‘managerial flexibility’, which becomes a central instrument for value creation. Real option framework takes this managerial flexibility into account. Therefore, it is more appropriate to use real option method to evaluate the project than the traditional DCF (discounted cash flow) tool if the firm has high volatility of the expected returns. In this study, we analyze the project evaluation using real option through case study about an IT firm that considers the investment of a project called as portal ASP(Application Service Provider). We use replicating portfolio approach, one of the applied binomial option pricing model, for option pricing and employ Monte Carlo simulation to estimate the standard deviation of rate of returns. This study finds the project that is rejected by DCF tool can be accepted if we use real option methodology. This result suggests that real option can be appropriate tool to evaluate the project if the firm has managerial flexibility under the uncertainty.