Critical thinking is an important way of thinking that should be taught in school and fostered throughout all levels of education, but it has been pointed out that critical thinking is not sufficiently developed in the science teaching methods learned by university students who aspire to teach elementary school. In this study, we devised and implemented a teaching method to cultivate critical thinking in science among university students who wish to become elementary school teachers. Specifically, we used a teaching method developed by Nakayama and Kinoshita (2022). After clearly explaining critical thinking in science, we had the students conduct problem-solving learning activities three times, utilizing the "CT (Critical Thinking) Application Sheet," which describes critical thinking methods, while having them self-evaluate their own thinking. After analyzing the results of the responses to the questionnaire before and after the class and the descriptions on the "CT Application Sheet" used during the class, it became clear that this instructional method was effective in cultivating critical thinking skills such as "reflective thinking" and "sound skepticism".