With the increasing attention on improving student achievement, private tutoring has been expanding rapidly worldwide. However, the evidence on the effect of private tutoring is inconclusive for education researchers and policy makers. Employing a comprehensive dataset collected from China in 2010, this study tries to identify the effect of private tutoring on student achievement in the National College Entrance Exam (NCEE) of China. This study finds that private tutoring has mixed and heterogeneous effects on mathematics, Chinese language, and English language respectively and on the NCEE total score. The average effect of private tutoring is not significant, but it may have a significant and positive effect on urban students with lower achievement or in schools with certain quality. Students from schools with more educational inputs are more likely to benefit from private tutoring. (Contains 23 tables and 4 figures.)