Purpose: The purpose of this study was to understand the experiences of mental health hospital workers. Methods: Participants in the study were a total of 8 mental health hospital workers who consisted of nurses, social welfare workers and health managers. To prevent them from being omitted, the interviews were all recorded under the participants prior agreement. The method was analysis using the phenomenological method proposed by Colaizzi(1978). Results: The experiences of the participants of this study were classified into 15 significant areas, from which 10 subjects hard work, conflicts, heavy feeling, irritability, getting familiar, changes of recognition, aptitude determination, feeling of achievement and sense of pride were drawn out. These subjects were then grouped into 5 themes. These five themes were finally grouped into 5 categories, negative emotion, depressive emotion, changes of thinking, delight and value discovery. Conclusions: The study tried to analyze the experiences of key informants like nurses, social welfare workers and health managers all of whom were serving at mental health hospitals, contribute to social recognition about the special medical establishment, promote qualitative mental health nursing and further provide educational information necessary for understanding mental health hospital workers.