The purpose of this study is to clarify a particular problem by analyzing the process of preparation for a mock class for learners in a music teacher training course. Interviews were held with four of the learners who had given the mock class, and data were written down as text data and analyzed by TEM. As a result of the analysis, the class preparation process can be divided into three phases: “I: Examining class content and preparation methods,” “II: Preparing lesson plans,” and “III: Examining classroom implementation methods.” The issues to be addressed in the classroom preparation process consist of the following four points: (1) the inability to anticipate students’ reactions; (2) the inability to help students learn at a deep level; (3) the inability to convey awareness to those with whom one is teaching; and (4) the bias in learners’ acquisition of knowledge in the process of preparing lesson plans and conducting the class. In the future, it will be necessary to study classes to overcome these issues.