This study aims to determine on what factors formed Electronic Word-of-Mouth (eWOM), to determine the effect factors of eWOM to buying intention, and to describe dominant factors of eWOM towards buying intention. This type of research is explanatory research with quantitative approach. The sample used the research was 108 people chosen with purposive sampling and data collection methods in questionnaire. Data analysis used factor analysis and multiple regression analysis. The results shows that five factors formed of Electronic Word-of-Mouth (eWOM) consist of Platform Assistance, Expressing Positive Feelings, Economic Incentives, Helping the Company, and Concern for Others. Those five factors has significantly effect towards buying intention. From this analysis concluled that Concern for Others is dominant factor formed Electronic Word-of-Mouth (eWOM).