In science, technology, engineering, arts, and mathematics (STEAM), hands-on making is the interplay of the sensuous forces of object-free and object-related intelligence transcendence in the continual process of quality improvement. The present research involved the design of a STEAM contest that focuses on having students use hand tools to produce three miniature models in the morning and then use these models to compete in relay races and tug-of-war contests in the afternoon. They were required to rely on their intelligence practice without the assistance of teachers or parents. Thus, this research aimed to explore the correlates between students' object-free (bodily-kinesthetic, spatial, logical) and object-related (naturalistic) intelligences, and their hands-on making self-efficacy (HMSE) reflected in their attitude toward quality improvement (ATQI) when participating in a STEAM contest. Data were collected from 330 junior high school students on the day of the STEAM competition and were subjected to confirmatory factor analysis with structural equation modeling. The results indicated that the students' 4 types of multiple intelligences were positively related to HMSE. Consequently, HMSE was positively related to ATQI. The results imply that ATQI was essential for students to win in the STEAM contest, which benefited those students with a high level of the 4 types of intelligence mediated by HMSE.