The purpose of this study is to develop and validate the evaluation indicators of teaching competency in STEAM education. The teaching competencies in STEAM education were drawn up utilizing both behavioral event interview (BEI) and a literature review. The initial evaluation indicators were then reviewed by 15 experts and two pilot tests were conducted. The revised version was administrated to 208 teachers, and the data from this survey were used to validate the factor-based model used in exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Final evaluation indicators of teaching competency in STEAM education were composed of 35 items in seven areas: Understanding of Subjects (five items); Teaching-Learning Methods (eight items); Inducing Learners to Participate in Learning (five items); Understanding of Learners (four items); Learning Environments and Circumstances (five items); Evaluation of Learners (four items); and Individual Qualification (four items). These evaluation indicators are a guideline on understanding what really matters in STEAM education and how to perform a STEAM class. Therefore, the results of this study can be standards of improving their STEAM classes by self-diagnosis, and used as consultation checklists for an effective STEAM class.