This study aims to develop and validate a STEAM children’s future competency measurement. A systematic literature review was conducted to collect and analyze STEAM-related literature, and seven factors comprising 50 items were constructed after review by external subject matter experts. We collected survey data twice from children aged 7–9 years old, with 413 responses in sample 1 and 425 responses in sample 2. Factor analysis (i.e., exploratory and confirmatory factor analyses), reliability test, and Rasch model analysis were performed. Eventually, seven factors comprising 43 items were validated. Based on the findings, we discussed the academic and practical implications, as well as suggestions for future research.