Sex education is a fundamental human right that is crucial for healthy human development, especially for elementary school students. The effectiveness of sex education largely depends on the level of competence of the teacher. Therefore, this study utilized the Delphi method to consult with experts and achieve consensus on the capacity and measures to develop the capacity of primary school teachers in sex education. Based on the results, this study proposes several measures to enhance the capacity of primary school teachers in sex education, including assessing teacher's capacity, developing content and methods for capacity building, and promoting the importance of sex education among teachers.