The purpose of this study was to differentiate the change in exercise behavior into different stages and to investigate differences in the process of change, self efficacy, decisional balances and depression according to the stages of exercise behavior change among middle aged women in Korea by using the transtheoretical Model. A convenience sample of 434 middle aged women (40-64 years) completed measures of all transtheoretical model constructs involved in exercise behaviors (stages and processes of exercise behaviors change, self efficacy and decisional balance) and depression. The data were analyzed by using the SPSS 10.0 program including descriptive statistics, and one-way ANOVA. The subjects were distributed in each stage of change in exercise behaviors: pre-contemplation (n=106; 24.4%), contemplation (n=126; 29%), preparation (n=88; 20.3%), action (n=51; 11.8%), and maintenance (n=63; 14.5%). The processes of change, pros(advantages of behaviors), self-efficacy and depression were significantly differentiated across the stages of exercise behavior change. Cons(disadvantage of behaviors) was not significantly differentiated across the stages of exercise behavior change. Results of this study suggested that discriminating of processes of change, self-efficacy, decisional balance, and depression could provide positive information to people about the stages of change in exercise behavior. Therefore, in designing interventions, the stage of a client's exercise behaviors change needs to be assessed prior to application of intervention programs in order to increase and maintain exercise behavior in middle aged women.