Currently, various luxury brand players are beginning to develop their own effective ways of communicating with and introducing their values to customers. Because of its effectiveness, i.e., providing easier access for keeping up with the constantly changing personal needs of customers as well as better economic feasibility in customer relationship management or maximizing customer satisfaction and brand loyalty, social networking services (SNSs) have become the most prominent communication medium for luxury fashion companies. This study focuses on the marketing application potential of SNSs by analyzing their influence on brand loyalty. The field research targeted subjects in their 20s and 30s who have experience with both luxury brands and SNSs. The 331 responses were analyzed by descriptive statistics, exploratory factor analysis, reliability analysis, cluster analysis, one-way ANOVA and multiple regression analysis. The results are as follows: First, an SNS could be summarized as having 4 characteristics: interaction, word of mouth, entertainment, and customization. Excluding the entertainment factor, the degree of influence SNS characteristics could exert on brand loyalty could be listed as interaction, WOM, and customization. Second, dividing SNS users into lifestyle groups, our research also examined whether the user's lifestyle affects the degree of SNS influence on brand loyalty. These user groups were the active leisure-oriented group, the ego-expression group, the fashion leader group, and the early adopter group. The active leisure-oriented group had a high proportion of young, high-income earners. Additionally, this group's members tended to use SNSs to check others' information and participate in communities for socialization. The ego-expression group had a higher proportion of females, and its members enjoy updating their pictures and sending personal messages. In addition, they showed a relative openness to disclose private information. The fashion leader group included a high proportion of females in their middle to late 20s and 30s. They possessed self-oriented and appearance-oriented values and stressed privacy. The early adopter group had a balanced ratio of sex and age. They had no aversion to digital equipment and thus actively used SNSs. Third, there were significant differences by user lifestyle in the relationship between SNS characteristics and brand loyalty. Specifically, the active leisure-oriented cluster perceived all SNS characteristics as highly important. The fashion leaders related reliability highly, which seems to result from their tendency to protect their privacy. In addition, all lifestyle groups, excluding the ego-expression group, showed that SNS characteristics had significant effects on brand loyalty. This study analyzed the characteristics of SNSs that act not only as communication tools among humans but also as new spotlighted promotion channels and determined which SNS characteristics influence luxury brand loyalty; therefore, this work also provided basic information for companies when planning social media marketing strategies. In addition, the present study is significant in analyzing SNS users' lifestyle groups to predict consumer behavior toward luxury brands' SNSs and in providing essential data to establish basic target marketing strategies by consumer segmentation.