The purpose of this study is to show the significance of incorporating the results of STS (Science, Technology and Society) into elementary school social studies environmental problem learning, and to develop and verify lessons focused on the “commercialization of science.” With “Minamata disease” as the core teaching material, we developed a fifth-grade unit, “Facing Minamata Disease,” based on the results of STS. The significance of incorporating the results of STS into elementary school social studies environmental problem learning is as follows. The first is that the learner can recognize the “commercialization of science” that exists in the background of environmental issues. Second, learners can think about how experts can face environmental issues as trans-science issues. Third, learners can think about how nonexperts can face environmental issues as trans-science issues. Additionally, the children’s note descriptions and analysis of class records revealed that the unit on “Facing Minamata Disease” is effective for children in Grade 5 in obtaining the above three points.