The purpose of the study is to find out the changes of Busan Nam High School, which is one of 10 Open-Autonomous Schools in Korea. An Open-Autonomous School is a reformative school model, which is endowed with considerable autonomy and diversity over the school management. This study is focused on two main research questions. Firstly, how was Busan Nam High School before it is operated as an Open-Autonomous School? Secondly, what kinds of school changes has Busan Nam High School experienced since it was designated as an Open- Autonomous School? To answer these questions, the changes of Busan Nam High School are divided into three categories: an input aspect, a process aspect and an output aspect. The effective indices of Hoy & Miskel(2001) are applied in analyzing these changes by using the methods of observation, interview and document analysis. The results are as follows. In the input aspect, human resources such as the school principal and teachers, procuring finances and organizing education curriculum have all changed. And in the process aspect, the motivation level of students and teachers has risen, effective leadership has initiated school changes, and various kinds of educational activities have been performed. In the output aspect, the attitudes of students have changed in a positive way and their level of satisfaction about school has risen.