The importance of a growing interest in the use of social network marketing is consistently accepted in luxury brand literature. Most social networking marketing literature and practice insist that social networking marketing efforts generate stronger brand equity, but some marketers have been disappointed in the effect of their social network marketing efforts. Overall, these findings show that the impact of social network marketing efforts might vary depending on the customers' traits such as social capital. This inconsistence with regard to social capital suggests the need for psychological factors to understand better social network marketing. This objectives of study is (1）to examine the determinants of purchase intention in luxury brands (2) to conceptualize social capital (3) to empirically investigate their impact on purchase intention. In order to test these hypotheses, we collected survey questionnaires from 295 customer who use social network services (e.g. Facebook, Twitter). All the measurement scales in this study from previous researches, with adaptations to fit the objectives of this paper. The estimate results from the structural equation model shows as follows: First, Bonding social capital positively affect social-adjustive function and, Bridging social capital positively impact on value-expressive function. Second, social-adjustive function positively is related to purchase intention. but, value-expressive function has no significant on purchase intention. Finally, the effects of bonding on purchase intention are mediated by social-adjustive function. In the conclusion, we suggest the theoretical and managerial implications of findings and discussed the limitations of this study.