本研究主要探討公司獨立董事忙碌是否導因於公司對獨立董事專業的需求或公司本身對外部資源的需求，以及市場對於公司獨立董事忙碌程度提高的反應為何。公司若想借重外部董事的聲望、專業、人脈、與經歷等資源，則獨立董事忙碌程度會愈高（董事專業假說）；當公司規模大或成長潛力愈高時，因公司屬於需求外部資源程度高的企業，故其獨立董事忙碌程度也會愈高（企業資源需求假說），實證結果支持上述兩個假說。當公司獨立董事忙碌程度提高時，市場會有顯著的負標準化累積異常報酬，且若董事忙碌是導因於公司追求專業獨立董事帶來之聲譽資本，市場會有顯著負向的反應。然而，公司規模愈大時，市場認同公司因監督管理難度較高應向外補給資源，使公司獨立董事忙碌程度提高，對標準化累積異常報酬有顯著正向影響（市場認同假說），實證結果也支持此假說。

This paper examines whether the need for professional independent directors or the need for external source is the cause of busy independent directors. We also investigate the market’s reaction to the busy independent directors. We hypothesize that the busy level of independent directors increases when the need for reputation, expertise, networks, and experiences brought by the independent directors is higher (director professional hypothesis). Since the need for external source is higher for larger firms and firms with higher growth potentials, we postulate that independent directors of these companies are busier than those of other companies (resource need hypothesis). Both hypotheses are supported by empirical study. When the busy level of independent director increases, the market shows significant negative standardized cumulative abnormal returns (SCAR). Moreover, if the business of the directors is due to the firm's need for the reputational capital brought by the professional independent directors, the market would have significant negative reaction. However, when the firm's size is larger, the market recognizes that the independent directors are busy because the firm is more difficult to monitor, which in turn results in higher need for external resources. Thus, for larger firms, the busy level of independent directors has a positive impact on the SCAR (market assurance hypothesis). This hypothesis is also supported by the empirical study.