‘Inability to switch off’,repetitive thinking about work,is considered to hinder work-life balance.The purpose of this qualitative research is to explore the construction and causes of ‘inability to switch off’. In this study,eighteen regular employees who engage in full-time work were interviewed. The data were analyzed based on grounded theory approach. The result shows that employees have their own ‘personal time’,when they want to switch off from work. It is also revealed that the employees feel psychological pain when they are stuck with recurrent thought about their work in their ‘personal time’. Based on these results,it is clarified that there are four forms of ‘inability to switch off’:‘affective intrusion’,‘worrying about their work’,‘being discouraged with themselves’ and ‘problem-solving pondering accompanied with pain’. Furthermore,the analysis reveals that each form has different patterns of relationships to the employees’ work environment,their cognitions,their behaviors and the degree of their personal life’s fulfillment. Although the generalizability of these results needs to be verified,this research is important because it reconstructs the concept of ‘inability to switch off’ and suggests the clues about how to prevent this inability,through closely examining working environment and individual cognitive and behavioral processes.