In this study, we considered the impact of acceptance of self and others, and knowledge of definition of developmental disabilities (basic knowledge) and knowledge to correspond to people with developmental disabilities (practical knowledge), on the university students’ attitudes toward people with developmental disability. 107 adolescences (46 men and 61 women, 18-25 years old) of this questionnaire survey completed the acceptance of self and others scale, questions of basic knowledge and practical knowledge, and attitudes toward people with disabilities scale. The results of hierarchical multiple regression analysis showed that attitude toward integrated education became negative, if practical knowledge is high, and acceptance of others is low. It was suggested that the personality characteristic that it is difficult to be able to accept others different from the their own, and empirical or potential negative images on the developmental disabilities due to low practical knowledge provide the negative impact on attitudes towards integrated education.