This study developed and validated a scale of STEM project-based learning (PBL) experience, which comprises four dimensions: scientific inquiry, technological application, engineering design, and mathematical processing. The participants were 727 primary higher graders. Both within-network and between-network approaches were adopted to analyze the construct validation of the scale. The within-network analyses revealed good internal consistency reliability. The four-dimensional structure of STEM-PBL experience was supported by the confirmatory factor analysis. Multi-group confirmatory factor analyses showed that the four-dimensional structure was consistent across students of different genders and grades. The between-network analyses generated significant correlations of the four dimensions of STEM-PBL experience with students' interest in learning STEM, utilitarian motives for learning STEM, and STEM career aspiration. This scale can be used in future research to probe how different components of STEM-PBL are related to the cognitive and affective development of students, which will in turn help teachers to make evidence-based decisions when they design STEM-PBL for different objectives.