Due to the expansion of the Internet, more people are learning through on-demand e-learning. E-mentor plays an important role in supporting learners in e-learning courses. In this research, we created an original questionnaire about the necessary attributes for e-mentors by: 1) describing the required attitudes and behaviors of e-mentors as well as the necessary knowledge and skills; 2) categorizing the responses; 3) creating 31 question items on e-mentor attributes from these categories; and 4) having 260 e-learners respond to the 31-item questionnaire. We conducted exploratory and confirmatory factor analyses to identify five factors that enhanced e-mentors' attributes. Factor 1, "Guidance to learners" comprised five items such as "E-mentor can help in precisely pointing out a learner's mistake." Factor 2, "Support for learners" comprised three items such as "E-mentor can give frequent feedback to questions posed by learners." Factor 3, "Consideration for learners" comprised two items such as "E-mentor can use words that do not confuse or demotivate learners." Factor 4, "Cooperation with teachers" comprised two items such as "E-mentors can work with teachers while consulting." Factor 5, "Motivating learners" comprised two items such as "E-mentor can offer support to motivate learners." Comparison of these factors with the face-to-face mentoring functions indicated that "Guidance to learners" and "Motivating learners" were common, however, "Support for learners" and "Consideration for learners" were unique to e-mentoring, while "Cooperation with teachers" was a factor unique to e-mentoring in Japan.