Due to people`s internet use growth and proliferation of ubiquitous technology, the internet addiction is becoming a social issue. However, the current adults` self-diagnosis measure about internet addiction, the K-scale, is a normal diagnostic method, which it does not consider user characteristics. In this research, we will propose a new internet addiction diagnostic method based on users` non-duty internet activities by using some questionnaire items to collect users` basic internet patterns used on duty related or non-duty related web sites. Since we simply ask for the basic internet usage pattern to each user who does not like to check frankly questionnaire items in the K-scale, the proposed method can find some hidden internet addicts compared to the K-scale with the SPSS statistical analysis tool.