This article considering the high portion and status of social network Facebook in the youth leisure and cultural consumption, has paid to study its effects and consequences on the youth social capital. In the theoretical section based on results of theoretical approaches and the review of accessible experimental resources, a conceptual framework has been set up and the researches hypotheses have been proposed in its format. This study has been done by survey method by using questionnaire with a sample population of 300 young people from Piranshahr. The results show that the time of youth membership in Facebook was 4 years and in average, they spend more than 3 hours in Facebook on a day. The main incentive of youth involvement in Facebook was leisure and identity issues and tendency to interaction and enlightenment are the other reasons. In terms of social capital, our findings show that the average of capital social among sample participants evaluated in average. The study showed that there is a direct relationship between using Facebook and social capital. However, the way which they use it and its intensity changes the relation. In the other words, the more the youth use Facebook, their social capital will decrease. The most reverse effect of Facebook is on youth political participation. Multivariate regression analysis shows that the youth social capital, respectively, are strongly related to variables of age, incentive use, economic-social status, length of membership and amount of using Facebook. The aforementioned variables determine 50% of changes in youth social capital.