The growth model of microorganism in the mixed substrates was presented on the basis of consideration of catabolite repression and enzyme induction. The application of the model to experiments with glucose and maltose as carbon sources in a batch culture and a continuous culture was examined. The calculated values according to this model were in satisfactory agreement with the experimental data in not only a batch culture but also a continuous culture. The stability of steady states in a continuous culture was analytically examined based on the eigenvalue. The number and stability of steady states appeared to vary with operational conditions such as dilution rate and feed substrate concentrations. The steady states can be classified into three categories: (1) a steady state where both substrates were consumed, (2) a steady state where only one substrate was consumed and (3) washout. To achieve a stable steady state where both substrates are consumed, the manipulated variables such as feed substrate concentration and dilution rate can be selected within a comparatively large area of values: dilution rate (0 to 0.7 h^-1) against feed maltose concentration (0 to 1 g/L) in the case of feed glucose concentration (0.3 g/L) and against feed glucose concentration (0 to 1 g/L) in the case of feed maltose concentration (0.7 g/L).