Objectives: It is known that the majority of middle schoolers spend the substantial amount of time using the Internet. Despite the fact, little is known about which factors are related to an increase in Internet use and what could be the consequences of excessive Internet use. The aim of this study was to explore factors affecting an increase in Internet use among elementary schoolers representing the population of South Korean elementary schoolers. Method: Secondary data obtained from the Korea Youth Panel Survey were analyzed longitudinally. Results: The average minutes spent using the Internet was 73.43 in the first wave, and was 92.17 in the second wave. Also, the percentage of those who experienced illegal behaviors on the Internet was 22.86% in the first wave, and was 30.92% in the second wave. Second, increased Internet use was strongly associated with an attack tendency, depression, suicidal ideation, stress, and delinquent behaviors. Finally, gender(being female), and increased attacking tendency, and smoking experiences successfully predicted an increase in Internet use one year later. Conclusions: It is necessary to provide education programs to young people and to develop preventive strategies for them. Through providing education programs, children can form desirable attitudes regarding the Internet use. Through providing intervention strategies, children can prevent from experiencing negative consequences due to excessive Internet use.