A Molded Case Circuit Breaker (MCCB) is an electric control device to interrupt the abnormal currents which result from the over-loads or short-circuits. Its malfunction will result in severe accidents. In the development of the MCCB, higher current-rating and improved thermal performance become more and more important in providing the safe function and reliability for the modern devices requiring small scale and high performance. It is also very important to consider the factors of temperature rise in the design of MCCB. The major reasons of temperature rise in the MCCB result from the resistances, which are come from the connection and contact surfaces. These resistances are influenced by current, time, configuration of contact surfaces and applied voltage. In order to predict the temperature distribution inside MCCB, we have simulated the model with some assumptions and simplifications, using commercial code ICEPAK. To verify the results of temperature field analysis, the numerical results are compared with experimental ones for the same model. The results show a good agreement with actual temperature rise obtained by experiments.