This study aimed at determining the relations among the ego-state, stress management and school adjustment of middle-school students. This study has asked 377 male and female middle-school students studying in Seoul and Gyeonggi-do and Busan and Gyeongsangnam-do to assess their ego-state, stress management and school adjustment. The results from the survey and its analysis are as follows. First, an assessment of the relations among the ego-state, stress management and school adjustment of a middle-school student showed that the ego-state of type A was the most proactive in solving problems as a from of stress management followed by types NP, FC and CP, while ego-state of type AC was a negative correlation. The ego-state of type CP showed a static correlation with school study, types A and NP with four sub-factors of school adjustment. Type AC showed a negative correlation with four sub-factors of school adjustment except for sub-factor "abidance by the rules". Two sub-factors of stress-approaching method under stress management were in a static correlation with four sub-factors of school adjustment. The suppression of inner emotions as part of stress-evasive stress management had a static correlation with factors such as school friends, teachers, and school life, whereas the expression of outward emotions had a negative correlation with the school life, while there was no significant difference with expression of inner emotions. Second, as a result of looking for the sub-factors of ego-state and stress management that are relevant to the sub-factors of school adjustment, a student with NP and A tendencies using a stress-approaching, stress management strategy successfully adjusts to school and enjoys school life. Based on the findings from the survey, this study came to the following conclusion; A student with an ego-state of types NP and A, who uses a stress-approaching method to manage stress, successfully adjusts to school, fully explores his/her intellectual capability, gets along with other people and is satisfied with school life. On the contrary, students with an ego-state close to types FC and AC have difficulties adjusting themselves to school as they take an evasive approach to stress management. These students need to participate in school programs or community-level programs to bring their ego-state closer to types NP or A and to learn to manage stress. An empirical education that takes place at school as well as at home would significantly enhance the effectiveness of such program. Finally, the limitations of this study and the suggestions for future studies were presented.