本篇論文的主要目的是檢測會計師是否會影響其客戶投資效率。本研究以2007至2016年間的中國上市公司為樣本，實證結果顯示:（1）事務所層級的產業專家對客戶投資效率有積極影響。（2）會計師個人、事務所皆為產業專家時相對於非產業專家可以提高其客戶的投資效率且其對客戶的投資效率的影響大於單一產業專家。（3）會計師個人、事務所皆為產業專家時，對於國有企業投資效率的影響小於非國有企業。綜上會計師在提高客戶的投資效率方面起著至關重要的作用。 / The objective of this thesis is to examine whether the auditors affect the investment efficiency of its client. Using a sample of Chinese listed firms during 2007~2016, I find that: (1) Audit-firm-level industry expert is positively associated with its clients’ investment efficiency. (2) Industry expert at both firm and partner levels has stronger effect on investment efficiency than industry expert, either at firm-level alone, or at partner level alone. (3) When auditors are industry expert at both firm and partner levels, the effect of industry expertise on investment efficiency is more pronounced for non-state-owned enterprises than state-owned enterprises. In sum, auditors play a critical role in enhancing firm’s investment efficient.