The purpose of this study was to investigate the current condition of self-directed learning(SDL), and analyzed significant variables explaining the SDL using a survey data at national level. The relationship between SDL and private tutoring was also explored through a cluster analysis. The results of analyses showed that high school students perceived their SDL low. The frequency of experiencing SDL was found to be 'sometimes'. As critical variables explaining the students' SDL ability, opportunities of SDL provided by teachers, caring student's level, and participation in extra curriculum activities were found to be statistically significant. Among these variables, participation in extra curriculum activities was the most significant variable. However, unlike the results of previous studies, private tutoring was not a significant variable explaining the variance of SDL. For a more valid understanding of the relationship between SDL and private tutoring, a cluster analysis was conducted. The results of analysis reported 4 different clusters reflecting the relationship between SDL and private tutoring. By analyzing the results of cluster analysis by background variables, a compound relationship between SDL and private tutoring was discussed.