In this study, the improvement of small DC motors used in automobiles was made through the evaluation of functionality. The functionality was evaluated by the relationship between the input power and consumed power. It was con sidered ideal that the power required can be obtained from the minimum power input. The power consumption during idle time was also studied. After the improvement of functionality, vibration and audible noise level were also significantly improved. Also by utilizing part of the gain of functionality improvement for the downsizing of motors, the cost and weight of motors were reduced. It is believed that the approach used in this study to evaluate the functionality of DC motors can be applied for the development of other motors towards the reduction of overall product development cost.