The purpose of this study was to investigate the effects of self-evaluating the causes of incorrect answers in TOEIC listening class. Students were supposed to submit self evaluation reports every week, take pre and post mock TOEIC listening test, and answer 5 survey questions. 19 students’ data were selected out of 28 students. This data was divided into two groups, diligent group(9) and lazy group(10) and analyzed. To achieve this purpose, four questions were asked. 1. Was it effective in improving students’ TOEIC listening score? 2. Was it helpful for students’ positive attitude for further learning? 3. What is an effective way of writing the report? 4. How effective was it for the researcher’s teaching activities? The results of data analysis were as follows; 1. Students’ TOEIC listening scores improved in both groups, so it cannot be said that it was a direct result from writing the reports. But, diligent groups got much higher scores in mid and final term exams. 2. The survey showed it was helpful for students’ having a positive attitude for further learning in both groups. 3. Student 9’s case showed how to write the report effectively, which was the only case of high improvement in the diligent group. 4. It was helpful for the researcher to organize class activities and understand and communicate with students.