The Purpose of this study was to build a substantive theory about the experience of psychiatric nurse. The qualitative research method used was grounded theory. The interviewees were twelve psychiatric nurses who had experienced. The data were collected through in-depth interviews with audiotape recording done by the investigator over a period of two years. The data were analyzed simultaneously by a constant comparative method in which new data were continuously coded into categories and properties according to Strauss and Corbin`s methodology. Analysis the grounded data resulted in 120 concepts being identified. Fifteen categories emerged from the analysis. The categories were motivation of application to psychiatric ward, conflict, caring for the psychiatric patient, desire for knowledge and skill, discover of valuing. These substantive categories are consistent with previous research results. Causal conditions included : motivation of application to psychiatric ward. Phenomena : conflict. Intervention condition : professional knowledge and skill, effort, support. Action/ interaction strategies : desire for knowledge and support. Consequences : discover of valuing. These categories were synthesized into the core concept ~ The process of conflict. The process of discover of valuing was proceeded by ① professional knowledge and skill ② effort for development, ③ support from others, ④ caring for the psychiatric patient. Three hypotheses were derived form the analysis. ① Psychiatric nurses who were poorly motivated when they applied for the psychiatric ward experienced more conflict. ② Psychiatric nurses who care for the psychiatric patient to the higher extent experienced less conflict. ③ Psychiatric nurses who had professional knowledge and skill experienced more conflict. This study will prove helpful understanding psychiatric nurses.