Facebook is a very popular virtual community in the world. When the Chinese version released in Taiwan in 2008, something interesting happened. People are not only interested in its powerful function for social network connectivity but also its online games such as Happy Farm. Due to its rapid growth in Taiwan, many enterprises also tried to cooperate with Facebook to market their products or services. However, few studies conducted understand the users motivation to enjoy this virtual community. To propose a framework to explain why people use Facebook, four focus groups were conducted, each with six participants. We found that effort expectancy, performance expectancy, perceived playfulness, social influence, perceived critical mass, human-message interaction, human-human interaction, information sharing, right of privacy protection, search function, free to use, and habit are factors influencing the behavioral intention to use Facebook.