Purpose of this study was conducted to investigate the factors influencing smartphone addiction of high school students. The data were collected from 351 high school students in B city and analyzed with t-test, ANOVA and multiple regression by using SPSS 18.0 program. The smartphone addiction rate was 20.8%, which the high risk group rate was 8.5% and potential risk group rate was 12.3%. The significant factors of smartphone addiction were using time in weekend, accident in using smartphone, aggression, depression, attachment to peer and behavior control of learning attitude. And these factors explained 33.4% of the variance in smartphone addiction. In conclusion, the results from this study indicated a need to develop the intervention program to prevent smartphone addiction.