This study investigates the effects of social media`s fashion advertisements. A survey was taken among men and women in their twenties who had experiences with fashion brand social media. A total of 270 questionnaires were used in this analysis. The results are as follows: First, the factors of content and pursuit of information had positive (+) impacts on advertisement attitude for both men and women in the fashion brand communities. Only the pursuit of information had positive (+) effects on men`s brand attitude; however, economy, self-satisfaction, and the pursuit of information influenced women`s brand attitude and purchase intention. Secondly, in fashion brand video UCCs, pursuit of information and the formation of relationships had positive (+) impacts on men and women, respectively. The formation of relationships had positive (+) impacts on men`s brand attitude; however, the formation of relationships and the pursuit of information influenced women`s brand attitude. The pursuit of information and formation of relationships had a positive (+) influences on men`s and women`s purchase intention, respectively. Men had differences in the pursuit of information and advertisement attitude in the two types of fashion brand communities and video UCCs; however, women had differences in economy and self-satisfaction, advertisement attitude, and brand attitude in the two types. The study results provide basic data by examining men and women in their twenties who have easy access to the Internet for advertisement attitude, brand attitude, and purchase intention in social media as an online fashion advertising media as well as useful information for establishing marketing strategies.