The objectives of this study were to make clear the awareness of Individual Teaching Plans (ITPs) of teachers in regular class, to extract the factors affecting awareness of ITPs of teachers in regular class, and to investigate these factors using causal models. This study focused on the environmental and individual factors. The former were organizational climate and organization structure of schools, both of which affect composition of ITPs, and the latter were years of teaching experience, teaching experience on special needs education, and experience on designing ITPs. A total of 384 regular class teachers in Japan were the subjects of this study. The results show that regulating degree of appropriateness reduces the burden teachers of regular classes feel surrounding their ITP, gives them confidence, and results in them perceiving it to a greater degree as one of their own work duties. Furthermore, the results of the examination showed that collegial atmosphere at the school and experience preparing ITPs increased their confidence and acceptance as their own work duties. It is important to provide them with training and establish effective collaboration system between coordinators and special school teachers.