證券交易法之重要規範，在於發行市場之真實性，與交易市場之公平公正性。而有價證券內線交易之禁止，為各國法制之重要一環，至於內線交易之討論，亦甚廣泛。惟對於內線交易重大訊息之具體要件與成立時點之界定，仍屬未能具體確定，具有研究之空間。本文乃針對此一問題，詳加探討。首先，就界定之法源與基本規範予以討論，再論及平等取得資訊原則與重大訊息傳遞，並就我國確定案件，自批判法學與實證法學之觀點，對於實務上認定「所得稅利益之認列」為重大訊息及該訊息之成立時點，詳加批判，再配合美國法制中之法律規範與案例，為比較法學研究。本文並整理歷年來我國法院裁判對於重大訊息之具體要件之認定標準，與判斷成立時點之原則，俾供學術界斟酌，期臻明確。

　　　　　The purpose of the Securities and Exchange Law is to ensure the accuracy in the issuing market, as well as fairness in the trading market. Thus the prohibition of insider trading of marketable securities is a major aspect of legislation in different countries. Although there are extensive discussions on insider trading, it remains difficult to clearly determine what constitutes "major information" and the instant at which such information begins to take shape; there is, thus, room for further research. This paper explores the above issues. First, this paper explores the legal basis of and basic regulations used for such determinations, and then explains the principles of equal access to information and dissemination of major information. Using actual case decisions in Taiwan, this paper critiques the determination of "listing of income tax benefits" as major information and the determination of the instant at which such information begins to take shape, from the perspectives of critical legal studies and empirical legal studies. A comparison is then made with U.S. laws and case decisions. This paper, likewise, compiles court decisions in Taiwan over the years to identify what constitutes "major information" and the instant at which such information begins to take shape, so as to serve as a clear reference for academia.