Providers for the commercial web sites are seriously competing for attraction and retention of customers. However, customer loyalty in the on-line business could be determined by factors different from those in the off-line business. In this paper, determinants for the customer loyalty in the on-line business are analyzed as two parts. The first part includes determinants that foster voluntary customer loyalty, such as satisfaction, self-involvement, and positive characteristics of Internet. The second part includes determinants that foster involuntary customer loyalty, such as switching barrier and bonds. Through the empirical study of 399 survey of Korean Internet users, both voluntary and involuntary factors contributing to the customer loyalty were found. Also, relationship between the positive characteristics of Internet and customer loyalty were found. The understanding of the determinants of customer loyalty will be an important information developing a winning strategy in the on-line business.