Social networking sites are created for help people to communicate with the others.Furthermore marketers have taken advantage of use these sites for profit; they have used these sites to promote their products and strengthen their existing brands.However, it was found that there was store-based social networks have increased.The shop on social network sites can sell products as well as profitable to the seller.Everything that happens in this trading may result from the trust.Starting from the relationship between friend to friend by the way they use trust to motivate purchasing intention.From the foregoing, we are focusing attention on the issue of trust and it has antecedents.Their antecedents that we was interesting in this research are cognition-based trust antecedents, affect-based trust antecedent and experience-based trust antecedent.　　This research aims to improve understanding of the reasons why people have a purchasing behavior impact of trust and its of buying through social networking sites, and to investigate the antecedent on the customers intention to purchase products.In this study we survey a representative sample of the members of the Facebook at Silpakorn University in Thailand.The results indicated that consumers trust was two important antecedents, cognition-based trust antecedents and experience-based trust antecedent.They have strong impacts on their purchasing decisions.Interestingly, the affect-based trust antecedent did not strongly influence consumers trust.