This study analyzed the effects of course evaluation methods on the validity of course evaluation. The online compulsory system, which most universities in Korea use in their course evaluation, would bring about the students' untrustworthy responses in course evaluation, that is, the rate over 50% of the consistent responses to every question of the course evaluation survey. The rate of the consistent responses to every question in the online compulsory system, which was administerd in the spring semester of 2009, and the one in the OMR card voluntary system, which was administerd in the fall semester of 2010, were compared. The result of the comparison was that the rate of the consistent responses to every question in the OMR card voluntary system was reduced sharply from 62.4% to 24.0%. Previous studies reported that the consistent responses in student ratings of college teaching is major threat on the validity of course evaluation, and in this context, the result of this study, which suggest a meaningful solution for reducing the ratio of the consistent responses, is valuable. Therefore, the OMR card voluntary system is recommended as one of useful methods for student ratings of college teaching.