According to the increase in the overall quality of the vehicle, the quality of customer actuated sounds also has become increasingly important. The folding mirror sound, which is one of customer actuated sounds, has less masking effect by driving sounds. Therefore, despite the low noise level, drivers may not be satisfied with the sound quality. The aim of this work is to identify sound quality factors which mainly contribute to customer's preference regarding the outside folding mirror. For this purpose, subjective evaluations were carried out and the sound quality index was developed through the statistical analysis. Next, noise source identification was carried out to reveal the contribution of motor excitation regarding sound quality. And then, development guideline in the viewpoint of the sound quality index, loudness and fluctuation term is suggested for improving sound quality.