The binomial option pricing model is widely used to understand pricing an option which is a financial derivative. The Model presents very important characteristics in deciding a price of an option. First, a value of option is decided independently with probabilities that stock prices are ascending or fall. Second, an option pricing is not depend on investors' risk preferences. When an option is evaluated, this paper may clear that investors had to consider the probabilities of a stock price's movements and their own preferences for a risk.