This paper reports the prevalence of Internet Addiction in Japan's adolescents. In autumn 2010, our research group made a statistical investigation on addictive internet use toward 1000 junior high school students in Tokyo city area. Statistical data on this topic is still now scarce in Japan. Therefore, this report itself may be valuable an information. We also analyze correlation between usage of internet services and degree of Internet Addiction. In consequent, services those are passive in communication (ex. weblog, video hosting service, online game) are revealed to be more strongly tied to Internet Addiction than interactive ones (ex. chat, e-mail).