In order to investigate how images of teaching change in the course of expertise, experienced teachers, novice teachers, students who took teacher education courses at the university, and students who didn't take them were compared on metaphor-making tasks. They were asked to make metaphors on 3 topics: “Lesson, Teacher and Teaching”. Both teachers and students made almost the same amount of metaphors. In the contents of the metaphors, however, there were some differences between them. Many students had images of teaching as transmission and routine work, and of teacher as teller. On the contrary, many expert teachers had images of teaching as joint construction with pupils and managing unpredictable situations, and of teacher as helper and supporter. These results suggested that students had explicit preconceptions about teaching before becoming teachers and their images of teaching changed with expertise.