This research used mixed effects to construct a PBL-STEM (problem-based learning with STEM) questionnaire with high validity and reliability. The benefits of PBL-STEM focused on cross-disciplinary and longitudinal research to analyze students' self-efficacy in life science. All 175 university students who attended this course as an elective participated in this research. The purpose was to evaluate students' performance in the cake-baking practice experiential course and to use unpaired samples t-test, one-way ANOVA, and feedback analysis as quantitative and qualitative data. The following are noteworthy results: The t-test showed that five stimulated scales were significantly different and better after the cake-baking PBL-STEM activity. In one-way ANOVA, to engage with more students in STEM activities, improve conceptual learning, and close achievement gaps. The more enthusiastic students are, the more actively they study and think, and the more effectively they improve their PBL-STEM learning. Students' feedback analysis of this teaching activity is beneficial for improving technology, student-teacher engagement, process comprehension, and learning interest. The light of this research will foster a disposition of learning, enhance cake-baking skills, and encourage problem-solving based on their thinking.