This study mainly aimed to explore the effects of project-based learning (PBL) integrated into science, technology, engineering and mathematics (STEM) activities and to analyze the creativity displayed by junior high school students while performing these activities. With a quasi-experimental design, 60 ninth-grade students from a junior high school in southern Taiwan were selected as subjects to participate in the six-week teaching experiment. The teaching design was centered on STEM activities and integrated with the strategy of project-based learning. The teaching contents included teaching materials integrating CaC2 steamship-derived knowledge of science, technology, engineering, mathematics, physics and chemistry as well as related teaching activities. Three conclusions were drawn. First, the key teaching points of the five stages of STEM project-based learning--preparation, implementation, presentation, evaluation and correction--can improve students' creativity. The learning objectives of STEM project-based learning can strengthen students' ability in STEM learning and STEM-integrated application. STEM project-based learning can further develop the affective domain of creativity, including adventurousness, curiosity, imagination and challenge. Based on the conclusions, this paper proposes suggestions regarding the implementation of STEM PBL activities to enhance the creativity and STEM-integrated application ability of junior high school students.