To encourage the creative design, hands-on, and problem-solving abilities of K-12 students, many countries have begun to set up makerspaces and promote maker education in schools. To help primary and secondary schools better implement maker education, this study explored the core competencies of teachers striving to engage or better practice maker education, investigating their perspectives on these core competencies and determining their competency levels. The study employed a two-step investigative approach: one, a focus group discussed and identified teachers' required knowledge and competencies; and two, an importance-performance self-assessment survey was conducted among teachers who participated in the Maker Education and Technology Center Program in primary and secondary schools in Taiwan. Descriptive statistics and analysis of variance were used in this study. According to the findings, the teachers generally recognized as important the core competencies the researchers discussed. However, the level of importance they assigned each item was high compared with their self-assessments of the core competencies, which suggests the need for better implementation of maker education. Successful maker education requires teachers to work in their professional fields, gain technology knowledge and skills, and build interdisciplinary connections to facilitate project-based learning. The results identified some principles to improve the professional development of maker educators.