The purpose of this study is to explore the positive and negative emotions that students have during manufacturing activities in junior high schools. Currently, STEM/STEAM education in Japan is being practiced on a trial basis with the aim of linking learning from various academic disciplines and applying it to solving problems in society. In particular, technology education that proposes concrete solutions is at the core of STEM/STEAM education. In order for students to be active, it is important for teachers to appropriately monitor and support students' emotional situations. In this study, an open-ended survey was conducted on 833 students in the 8th and 9th grades of junior high school who participated in manufacturing activities using wood, regarding the situations in which positive and negative emotions were generated in various manufacturing situations. As a result, valid responses were obtained from 788 students. When the responses were tabulated, 95.6% of the students had positive emotions and 87.2% had negative emotions during the manufacturing activities. As specific activity situations, sawing and nailing showed that they were also likely to have positive and negative emotions. The students who were behind in their work had positive emotions because they were helped by other students. On the other hand, the students who helped did not have positive feelings. The situations in which students were most likely to have negative feelings were when materials were damaged, when dimensions did not match, or when the work was not completed on time. It is important for teachers to provide appropriate support in these situations.