自1999年我國新增修正式無保留意見之簽證類型之後,此類型之審計意見即逐年增加。我國增加此簽證類型是否影響投資人對企業的評價,或改變投資人對會計師簽證的認知,是一個待探討的問題。本研究以台灣上市櫃公司為樣本,以1999年分界,比較1996至1998年及2000至2002年兩段期間,投資人因審計意見之差異而對企業評價及會計師簽證的影響。實證發現,在新增修正式無保留意見之前,投資人對收到保留意見的公司有顯著的負向評價;而且對收到保留意見次數越多的公司,負向評價越大。此外,投資人對四大會計師事務所查核公司之評價顯著優於非四大會計師事務所。在新增修正式無保留意見之後,投資人對收到修正式無保留意見與無保留意見公司的評價並無顯著差異,且對四大會計師事務所查核公司亦無較高之評價,顯示新增修正式無保留意見並不影響投資人對企業之評價,而且無法凸顯四大會計師事務所的簽證價值。由於按我國之規範,有六種情況會計師可出具修正式無保留意見,本研究進一步分析投資人在各情況下之修正式無保留意見與無保留意見之差異。因樣本量限制,僅比較「採用其他會計師意見且欲區分責任」之修正式無保留意見與無保留意見之差異,仍得到類似的結論。 In 1999, CPA could issue a new attestation opinion, modified unqualified opinion (MUO), in Taiwan. This regulation change induced CPAs to issue MUO more and more annually. It is an essential issue whether this regulation change will affect investors' evaluation for business value or change the cognition for CPA’s attestation. This study took the companies listed in TSEC and OTC as samples to examine this issue. The year 1999 was used to be a cut point and compared two samples, 1996-1998 and 2000-2002, for the difference about investors’ evaluation of business value and the cognition of CPA attestation. The results indicated that before MUO was issued, business value would decrease if companies received qualified opinion. Moreover, business value would decrease more if the companies received more times of qualified opinion. It also found that the companies have higher value if they were audited by big 4 than non-big 4 CPA firms. After MUO was issued, the business value was no significant difference if they received MUO or unqualified opinion. It was also no significant difference for business value if companies were audited by big 4 or non-big 4 CPA firms. It reveals that MUO was no difference to unqualified opinion. And the regulation change for attestation opinion had harmed the attestation value of big 4. According to the regulations in Taiwan, there are six cases that CPA can issue MUO. This study analyzed thoroughly the difference between MUO and unqualified opinion in all the cases. For the limitation for samples, it could only compare the case which relied on another auditor’s opinion and unqualified opinion. Still, the conclusion was the same.