Virtual reality (VR) and augmented reality (AR) are revolutionary technologies extensively used in science education. However, there has been insufficient discussion of teachers' expertise in using VR/AR. This study explored how pre-service teachers use VR/AR technology in science education based on the technological pedagogical and content knowledge (TPACK) framework. We analyzed the discourse data of pre-service teachers' lesson planning and post-lesson reflection discourses on their microteaching using epistemic network analysis (ENA). ENA overcomes the limitations of the existing TPACK research, which analyzes each element of TPACK separately and does not conduct an integrated analysis. The results showed a complementary relationship between the two discourses. TPACK elements not sufficiently considered in lesson planning caused problems in microteaching and were discussed intensively during lesson reflections. The pre-service teachers focused on VR/AR content, curricula/textbooks, and classroom management in their planning discourse, device use, and learners' reflection discourse. Based on these findings, we discuss methods to develop and enhance pre-service teachers' TPACK and promote teacher education using VR/AR in the classroom. Teacher educators should support pre-service teachers by considering the various TPACK connections in lesson planning. Additionally, they should provide a list of VR/AR content that is appropriate for the curricula to reduce pre-service teachers' time spent searching for appropriate content.