Creativity is an important capability in the 21st century that human beings need to have in order to meet complex future challenges. It also plays an important role in integrated STEM lessons (science, technology, engineering and math) development according to the technical design process. Therefore, it is essential to have a tool to evaluate creativity in the technical design through STEM lessons. Our research aims to design such kind of tool, Data used in this research was collected from 160 high school students in the North and Central of Vietnam. In order to determine the value of the scale, reliability analysis, discovery factor analysis (EFA) and confirmatory factor analysis (CFA) were utilized. The results of the analysis show that the tool has high reliability and appropriate value to use in creativity assessment. By using this tool, students can assess their own creativity in technical design. Further research direction is also proposed in the conclusion section of the article.