The purposes of this study were to examine the smartphone addiction level of middle school students and to analyse the effects of related variables like as individual, family, school and peer variables for providing the basic informations about prevention of smartphone addiction. For this purpose, the surveyed data from 345 middle school students in Gwangju were analysed. The results of this study were as follows. The smartphone heavy users were 203 students, it was appeared to reach a significant level of 58.8%. In time of smartphone using per day, 1-2 hours was 24.9%, 2-3 hours was 25.5% and even more than four hours was 17.1%. The variables affecting the smartphone addiction level of middle school students were gender, smartphone use time, smartphone preference in sociodemographic and smartphone use variables. Also depression in individual variables, intimacy with parents in family variables, and low academic performance in school variables were significantly important in effects on smartphone addiction level. Therefore, in order to reduce the addictive use of smartphone of juvenile, an integrative intervention and systematic strategies are required.