The purpose of this study was to describe the swimming instructors’ difficult in the field adaptation. To achieve this purpose, qualitative case study was conducted for 10 swimming instructors who was working at public sports facilities located in Seoul. Data were collected through in-depth interviews, participant observation, and documents were analyzed using Spradley’s(1980) cultural analysis method. During data collection and analysis, data were continuously verified for reliability, validity and ethics. The swimming instructors’ difficult in the field adaptation consisted of the instruction, human relations, administrative job, manager’s perception, conflict with other departments, and social perception.