The main objective of this study was determine why employees conduct non-work related smartphone use at work. To do this, this study developed the research model of non-work related smartphone use behavior consisting of factors such as habit, intention, social effect, task interdependence, and behavior. And it was tested via a survey of employees using smartphones. The results of this study reveal, first, that habit and social influence are significant predictors of non-work related smartphone use behavior. Secondly, task interdependence has a positive moderating effect between intention and behavior in non-work related smartphone use.