The purpose of this study is to investigate the relationship between depression and ego identity of middle-aged women and to identify the variables that show differences in the depression and ego identity of middle-aged women. The subjects in the study were 321 mothers of high school students whose age were 40-59 years old. The instruments for this study were Beck Depression Inventory(BDI) developed Beck(1978) and translated by Lee(1981) and Ego identity Scale developed Suh(1975) and modified by Nam(1975). The reliability values of BDI range from 0.83 to 0.87 and Ego identity range from 0.81 to 0.85 using Cronbach alpha. The data were analysed by using the SAS program and included Frequency, percentage Pearson Correlation MANOVA, t-test, ANOVA. The conclusion obtained from this study were as follows ; 1) There was a negative correlation(r=-0.21, p=0.0002) between depression and ego identity of middle-aged women. Thus the lower depression the higher ego identity for middle-aged women. 2) According to the analysis of interacting effects of depression and ego identity, there were significant differences in the household income(F=0.38, p=0.0035), level of education (F=6.50, p=0.0001), satisfaction of marriage(F=10.45, p=0.0001), family pattern (F=6.18, p=0.0001), menopausal status(F=7.23, p=0.0001), present disease(F=4.85, p=0.0110) and health status(F=9.00, p=0.0001). 3) There were significant differences on the level of education(F=12.98, p=0.0001) household income(F=5.78, p=0.0007), support of spouse(F=8.58, p=0.0002), satisfaction of marriage(F=20.08, p=0.0001), menopausal status(F=11.32, p=0.0001), present disease(t=2.76, p=0.0062) and health status(F=17.23, p=0.0001) of the depression of middle-aged women. 4) There were significant differences on the patterns of household(t=-2.64, p=0.0086), support spouse(F=3.58, p=0.0291), satisfaction of marriage(F=3.90, p=0.0212), menopausal status(F=4.59, p=0.0108) and disease(t=2.11, p=0.0359) of the ego identity of middle-aged women. On the basis of the above findings the following recommendations are made ; 1) According to results of this study, middle-aged women's depression is correlated with ego identity. Thus when the nurse plans the preventive strategy of middle-aged women's depression, the nurse must be considered with level of ego identity. 2) To study for middle-aged women in depth, further research is need to study regard to middle-aged men and their children.