近來陸續爆出的舞弊案件已連帶引起了社會大眾對關係人交易行為的注意。本文先探討審計品質與關係人交易之關聯性，而實證結果顯示關係人銷貨、進貨、應收款項與應付款項交易與審計品質皆呈負向關係，足見關係人交易之查核是困難的。因此本文期望透過外部審計人員的專業屬性來降低關係人交易對審計品質產生的不良影響，提升投資人對公司財務報導的信任。過去文獻針對會計師專業屬性部分，指出會計師事務所規模愈大以及產業專精程度愈高者，具備較佳的查核品質。研究結果顯示當關係人銷貨、進貨及應收款項交易係由四大會計師事務所或產業專家會計師事務所查核時，因大型會計師事務所或產業專家會計師事務所具備較佳會計師專業屬性，能抑制或減少關係人交易對審計品質之負面影響，而提升財務報表之審計品質。 / Numerous financial reporting frauds over recent years have made related party transactions the center of public attention. We first investigate the association between related party transactions and audit quality (proxied by discretionary accruals), and find that four kinds of related party transactions (including sales to related parties, purchases from related parties, accounts receivable from related parties and payable to related parties) all have negative impacts on audit quality. We posit that (1) external auditing is a monitoring mechanism to reduce audit quality decline caused by related party transactions, and (2) auditor attributes including big 4 audit firms and industry specialist audit firms can mitigate the audit quality decline thereof. Empirical results show that companies audited by big 4 or industry specialist audit firms, whose sales to related parties, purchases from related parties and accounts receivable from related parties show significantly smaller negative impacts on audit quality than companies not audited by big 4 or industry specialist audit firms.