我國現行證券交易法對於證券詐欺行為之規範以第二十條為主。若原告欲依該條文提起證券詐欺之訴訟，必須證明其所受之損害與被告的虛偽、詐欺或其他足致他人誤信之行為間具有信賴與因果關係存在，始能獲得救濟。然而，以我國現今證券市場的型態，證券市場上影響股價的因素甚多。受害投資人在證券詐欺訴訟中欲證明其損害與被告的詐欺行為間具有直接的信賴與因果關係存在，實屬不易。因此，造成受害投資人難以透過民事相關程序獲得救濟，進而證券交易法第二十條亦未能發揮預期的功能。 以往，美國法上也會面臨相同的困境。經由美國實務界發展出所謂的「市場詐欺理論」，該理論減輕了受害投資人在證券詐欺訴訟時關於信賴要件與因果關係的舉證責任，使得訴訟較易成立。進而達到證券法規保護投資人的目的。而我國證券交易法第二十條之立法，基本上乃仿效美國一九三四年證券交易法第十條b項及Rule10b-5而來。透過對美國法的比較研究，可為原告在證券詐欺訴訟中舉證責任所面臨的困境尋求可能的解套方案，使得我國證券交易法第二十條能夠發揮應有的效果。 本文首先概述我國證券交易法第二十條關於證券詐欺行為之規範，並指出受害投資人在證券詐欺訴訟中信賴要件與因果關係之舉證所面臨的困境。接著，介紹美國證券法規對於證券詐欺的規範及其實務見解，並探索「市場詐欺理論」的基礎原理。最後，藉由分析我國引進此理論的可能性，並建議在現階段可以法官造法的方式參酌「市場詐欺理論」的原理，採取信賴要件與因果關係推定存在的方式，以減輕原告的部分舉證責任，以發揮證券交易法第二十條應有之功能。

For a successful securities fraud action under Article20 of the Taiwanese Securities and Exchange Act, a plaintiff must establish the relationship of reliance and causation between his injury and the defendant’s wrongful conduct. However, the legal system in Taiwan is limited by the difficulty of proving the requirement of reliance and causation in a securities fraud action and, therefore, cannot efficiently enforce Article 20 of the Taiwanese Securities and Exchange Act for its intended purpose. Accordingly, how to establish the requirement of reliance and causation is an important issue for a securities fraud action under Article 20 of the Taiwanese Securities and Exchange Act. Similarly, Rule 10b-5 of the Securities Exchange Act of 1934 is also regarded as the most important antifraud provision under American securities laws. In order to establish the requirement of reliance and causation in securities fraud actions under Rule 10b-5, the U.S. courts establish the so-called “fraud on the market theory.” In the securities law area, because the Taiwanese Securities and Exchange Act emulates the American model, the exploration of the American experience in establishing the requirement of reliance and causation in a securities fraud action under Rule 10b-5 may provide a reference for Taiwan to establish the requirement of reliance and causation under Article 20 of the Securities and Exchange Act. This article will discuss the problem faced by Article 20 of the Taiwanese Securities and Exchange Act, explore the similar antifraud provision in the U.S. (Rule 10b-5), address the fraud on the market theory to establish the requirement of reliance and causation in securities fraud actions, and offer the suggestion for establishing the requirement of reliance and causation under Article 20 of the Taiwanese Securities and Exchange Act.