The purpose of this study is to examine factors that affect academic achievements of international students. Based on the factors, moreover, this paper finds out the way to improve academic achievements of international students. A questionnaire survey method is used on this paper in order to achieve the purpose of the study. The paper departmentalized and surveyed the factors: Korean language competence, lecture content, comprehension, understanding on teaching materials, attendance, lecture focusing, activity participation, assignment submission, preview and review, lecture satisfaction, lecture recommendation, etc. According to the result of analysis, other factors except preview and review were statistically meaningful throughout these ten factors. Furthermore, the paper analyzed correlation with each variable. The most relevant factor to academic achievements was assignment submission. However, assignment submission necessarily involves understandings of lecture content and teaching materials thus Korean language competence is not the most influential factor on academic achievements but Korean language competence to carry out studies may leads enhancement of academic achievements. Therefore, international students should acquire not everyday Korean, but Korean for academic purposes. Since contemporary university education demands courses and assignments which are performed on group, especially, communication education should be essential in order to enable free communication with teammates. Development and operation of programs which solve problems on assignments and reports may also help advancement of international students’ academic achievements.