The suitability and characteristics of middle school inquiry activities in the 2015 National Curriculum of Science in Korea were studied from the perspective of eight science teachers with rich experience in teaching science inquiry activities. In-depth interviews revealed problems teachers experienced while conducting inquiry classes. Problems were classified into five categories: inquiry level, method, tool, inquiry result, difficulty in guidance, and safety. Based on this analysis, strategies for an inquiry improvement plan are suggested, including that quantitative inquiry requiring numerical interpretation of data obtained from the process of inquiry should be emphasized. Concrete guidance of inquiries should be provided for non-major science teachers to help them instruct inquiries more easily. Institutional improvement is needed to develop curriculum activities and the improvement of science lab and classroom environments are necessary for conducting inquiry activities utilizing technology. The results of this study can contribute to the development of science inquiry activity programs.