We apply Bass's diffusion model to estimate and forecast the demand for electronic payment. Electronic payment is so popular in recent days that almost everybody uses it without difficulty everyday. As a result, its accurate prediction is very important for financial institutions and firms in information technology industry because they have to spend large amount of money to prepare the expensive equipment to provide electronic payment service. When we examine the electronic payment market and estimate the diffusion model, we find several important facts. First, individual electronic payment increase very fast when it is first introduced and later it become stabilized and saturated at a certain point. Second, applying diffusion model, we find the models fit very well by interpreting the R2's of the estimated equations or significance levels of estimated coefficients. Third, by simulation analysis, the forecast value track the actual one very closely in many cases. In conclusion, we may say that the diffusion model can be useful to predict the electronic payment.