This research attempted to examine the influence of the public library on our society and its relationship with social capital. For this research, a theoretical approach to the relationship was required. This approach enabled the research to analyze the type and range of the social capital being studied. In addition, this research emphasized that the social influence of public libraries was equivalent to the influence of social capital, based on the interaction between individual and community. The research outlined the mechanism by which public libraries create social capital. Finally the findings of this research were expected to help to develop an effective policy for public libraries.