Social commerce and social shopping communities are growing in number and size, and companies which are using social commerce can increase the market share at a small charge. Customers are interested in the social commerce because of purchasing products or services at a low price. Social commerce is also a more recent phenomenon and has not been studied as extensively. Thus, this study investigates customers' acceptance of social commerce based on the Technology Acceptance Model(TAM). The purposes of this study are as follows. First, we understand that perceived risk of social commerce is a multidimensional concept, and study the relationship between attitude and perceived risk such as the economic risk, social risk, psychological risk, risk of time-loss, privacy risk, source risk, and risk of time-limit. Second, we analyze the relationship between perceived ease of use and attitude, and the relationship between perceived usefulness and attitude of social commerce. We also examine the relationship between perceived usefulness and the perceived ease of use, and the relationship between the attitude and behavioral intention of social commerce. Third, this study investigates whether perceived usefulness and attitude have a positive effect on behavioral intention of social commerce depending on the collectivism. In order to carry out research purposes, we conducted a survey of social commerce users,obtained a total of 243 questionnaires, and did a path analysis and moderated regression analysis. The research results are as follows. First, the perceived risk in social commerce had a positive influence on the attitude toward social commerce. Customers' damages are increasing because ailing companies introduce on the social commerce. For example, it is difficult to cancel or return the coupons after customers purchased on social commerce. Thus, customers perceive lots of risks about social commerce, and the risk factors can negatively influence the attitude toward social commerce. Second, the perceived ease of use did not has a positive effect on the attitude, but the perceived usefulness toward social commerce had a positive effect on the attitude. Third, the perceived ease of use positively influenced the perceived usefulness,and the attitude toward social commerce positively influenced social commerce usage intention. Finally, the relationship between perceived usefulness and usage intention was moderated by the collectivism. Social commerce is a kind of group purchases. Thus, customers who pursue collectivism culture use more the social commerce for purchasing because they perceive more useful on social commerce than other people. Customers who have a positive attitude about social commerce will purchase products or service on the social commerce. Because the social commerce is still in its early stages, and there has been minimal research regarding social commerce, this study can provide the theoretical framework for future researches of social commerce, and various contributions when companies relating to social commerce establish advertisement and promotion strategies.