This study concerned teacher education in mathematics―specifically, curriculum resources (textbooks and other media that teachers use when planning a lesson or delivering classroom instruction). Four levels of curriculum resources (media) were identified, and the concept of “translation” was adopted to describe the process in which a medium at a higher level is replaced by a medium at a lower level. A survey was conducted among 15 trainee teachers in the 2019 academic year. The purpose of the survey was to examine inter-teacher differences in lesson planning; particularly, the media the teachers used in their translations, the order in which they used the media, and how each medium shaped the translation process. The results revealed that (1) the trainee teachers simulated the actions of the textbook authors or students and that (2) the functions of the media changed after a translation was performed. These findings imply that differences in lesson planning can be explained by differences in the type of media translated, the order in which they are used, and the way the media are used.