This research was to examine the understandings of elementary school teachers on the phenomena related to light and image, and to survey their perception change related to learning contents of optics. The subjects were selected from the elementary teachers who were enrolled in a graduate course, 'Science education seminar' at an education college located in Chungchungbuk-Do, South Korea. Among the five students who exposed their perceptions clearly in the class, the three of them were selected who agreed to the proposal of the case study. To achieve the purpose of this study, semi-structured interviews following the conception test with the 3 elementary teachers were conducted. During the analysis of the data, additional interviews by phone, e-mail, and internet messenger were conducted if necessary. According to the results, all of the elementary school teachers lacked the scientific conceptions of the phenomena related to light and image. Unfortunately, their learning experiences did not help them to understand the scientific concepts. During the interviews, the teachers recognized the importance of the viewpoints of seeing, image, cognition of light, point light source to understand the phenomena related to light and image.