User interface design for cross-ethnicity is quite common and one that would be benefited by this issue is e-Commerce. An e-Commerce which considers this issue seriously would be able to gain more interest from people, especially the people coming from rural areas where e-Commerce has not been able to reach them yet. The purpose of this study is to find out how far ethnics' culture is able to affect an e-Commerce user interface design process. Hofstede's cultural dimension questionnaire on Indonesian ethnics and an open-ended questionnaire were given to Indonesian e-Commerce consumers to acquire deeper information about the ethnics' preference. Three major ethnics in Indonesia were selected based on the respondents' cultural background. The result of these surveys then was used as a guideline to develop an e-Commerce site prototype which was later tested using usability testing methods. Based on the questionnaire and the usability testing result, we found that the three main ethnics have a similar preference and the same characteristics on e-Commerce user-interface.