In this research, online-education was given to Korean 6th grade underprivileged students, then education efficiency was analyzed. In order to carry that out, education result based on the teaching method in online-education was analyzed. The teaching method was divided into two, one with both online mentor and offline teacher helping and the other with just the online mentor. As a result, help of both online mentor and offline teacher showed higher achievement in education performance result, online-education participation rate, and assignment completeness. Therefore help of both online mentor and offline teacher is more effective in online-education of underprivileged elementary students.