Recent studies of online consumer trust have focused on trust in either a Web site or an online retailer. However, customer attitude may differ by the type of avatar, because customer trust can be cognitive or emotional. Moreover, customers may depend on their own product knowledge for judgment and decision-making. An online survey of female consumers with two scenarios about skin care products was conducted, and 599 responses were used to test the research hypotheses. The result indicates that avatars can indeed increase customer trust in e-commerce. It also finds that different types of avatar elicit different types of customer trust. Customers have higher cognitive trust in the expert avatar than in the attractive one, and customers have higher emotional trust in the attractive avatar than in the expert avatar. It was also found that an avatar is effective for customers with either knowledge or low product knowledge, while the effect of the type of avatar on trust is stronger for customers with high product knowledge. The effect of emotional trust on purchase intention is stronger than that of cognitive trust. For cosmetic skin care products, attractiveness may be more important than expertise factors when designing the avatar for an online retailer, and an attractive avatar may be the reference point of consumer's ideal vision of herself.