The purpose of this study is to investigate one preschool pre-service teacher on her teaching beliefs, development of the teaching beliefs, and factors affecting the teaching beliefs. Qualitative research method was used for case study. Data were collected by naturalistic observations, in-depth interviews, and documentary analysis. Following results were found after one and half years of research: (a) The contents of teaching beliefs of the preschool pre-service teacher included primarily the following: belief of educational purpose, belief of teacher-student relationship, belief of arranging teaching courses and activities, belief of classroom management, and belief of teaching method. (b) Due to influence of early experiences, preschool pre-service teacher developed her teaching beliefs right after her enrollment in teachers colleges. (c) The preschool pre-service teacher's development of teaching beliefs under the influence of early experiences showed clearly after teacher education course. (d) Factors affecting the preschool pre-service teacher's teaching beliefs included the early experiences, teacher education courses, relevant publication, and the experience of observation and practice.