This study investigates how to develop the teaching competence of Korean language student teachers and explores the variables that influence their practice teaching. The research participants were four student teachers at three secondary schools, and data were collected from observations, interviews, and documents. The primary data are from observations of instruction and interviews with the student teachers. The key term extracted from the data of the four student teachers is “growth of the teaching competence of Korean language student teachers.” The variables that influence practice teaching are the perception of practice teaching, experience of real instruction, experience of problems, and factors related to teaching competence. The teaching competence of Korean language student teachers develops through their experiences of practice teaching. Student teachers expect to practice teaching and have the responsibility to do so, and the experience of giving real instruction is most related to the growth of their teaching competence. However, student teachers experience problems stemming from the confusion of their internal identity and external environmental effects. The teachers’ instructors and university lectures are environmental effects. To foster the growth of Korean language student teachers’ teaching competence, the education of student teachers and practice teaching should ensure internal stability focused on teaching competence.