The opinions of pre-service science teachers about activities based on engineering design process in the STEM education were analyzed in this research. Eight volunteer pre-service teachers studying in the second year of the Science Education program participated in the study conducted with the case study design. Pre-service science teachers designed their own vernier caliper and micrometer in the activities, which was prepared by the researchers based on the engineering design process in the STEM education. In these activities, pre-service teachers followed the engineering design process steps of identification, research, imagination, planning and creation, testing and development, and communication. Following the research, all of the pre-service science teachers expressed positive opinions about the activities, while six pre-service science teachers expressed both positive and negative opinions. The positive opinions focused on the cognitive effects of the activity, including the need use imagination, develop creativity, the support provided to visual memory, envisioning what to do, applying reason and generating new ideas. The six pre-service science teachers who expressed negative opinions focused on the time taken for the activity, the difficulty in constructing the measuring tool, the inadequate functionality, the errors produced and cannot always be used.