This study examined the mediated effect of stress coping strategies in the relations between interpersonal relationship and internet addiction of university students. A total of 425 university students(236 were male, 189 were female) participated in this study. The methods of measurement are Adult Internet Addiction Scale(Sun-mook, Lee, 2005), IPPA, Stress coping strategies scale. It employed statistical analysis, correlation, regression and multi regression analysis using SPSS 15.0 win in order to investigate how interpersonal relationship was related to internet addiction. The result showed followings. University students mostly use internet at home, spend the time in searching information. The nagative aspects of internet useage are overfatigue, study failure, interpersonal problems and so on. Interpersonal relationship of university students and stress coping strategies are related to internet addiction. Futhermore, interpersonal relationship of university students effected internet addiction partially mediated by passive stress coping strategies. If university students have bad communication skills, distrust their friends in relationship, they have passive coping strategies in stress, so that they have more risk of internet addiction. Therefore interpersonal relationship of university students directly influenced internet addiction, also influenced by passive stress coping strategies. In future, developing a program for internet addiction of university students should be considered that stress coping strategies must be included. Limitations of the current study and implications for future study and counseling practice are discussed.