Providers for the commercial web sites are seriously competing attraction and retention of customers. However, customer loyalty in the on-line business could be 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, 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 Korea 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 input to develop a winning strategy in the on-line business.