The purpose of this study was to analyse the factor of the variables that contributed to the ego-identity of middle-aged women. The subjects were 751 middle-aged women whose age was from 40 to 60 years old. The instruments used in the study were the assessments of ego-identity, self-differentiation, and internal systems. The data were analysed by using pearson correlation and hierarchical multiple regression. The findings were as follows; (1) In the result of the analysis about relationships with ego-identity, the ego-identity was positively correlated with self-differentiation and the self of internal systems and negatively correlated with the parts of internal systems; (2) Predictors of ego-identity of the middle-aged women ordered occupation type, the level of education, cognitive-emotional function, self integration, family projection process, self, pleasing/abandoned part, and self-harming part. Based on these results, the recommendations for the future research in this area were discussed.