近年來假訊息造成影響的嚴重程度，足以改變一國選舉的結果。2020年美國大選，假訊息戰益發慘烈，導致各新聞媒體、網路社交平臺採取自律措施，防止假訊息擴散。惟自律措施卻引發侵害言論自由的爭議，假訊息議題有深入研究的迫切需求。本文第一部分，探討文書與網路訊息的差異，從文書特性來比較網路訊息的法律意義，再從偽造文書罪與行使偽造文書罪行為來理解假訊息行為，但網路特性的影響力遠遠超越文書，其定義仍有進一步釐清的必要。第二部分，從分類上定義假訊息，依訊息之內容、行為人之行為態樣為分類，分為偽造訊息行為、誤傳假訊息行為及假新聞行為，接續比較網路世界與實體世界的言論自由保障，並從日、美二國司法實務見解探討匿名言論保障及對新聞媒體的「編輯裁量權不可侵犯性」原則探求新聞自由。第三部分則探討現行以危險犯的立法模式，採取管制措施產生的效應，是否會侵蝕現代民主法治，牴觸刑法謙抑性原則、罪責原則。最後則是綜合對假訊息犯罪的主題，從立法到自律原則，提出本文研究心得與建議。

The severity of the impact of false information in recent years is sufficient to change the outcome of a country's elections. In the 2020 U.S. election, the false information war has become fierce, causing news media and online social platforms to adopt self-regulatory measures to prevent the spread of false information. However, it has triggered controversies that violate freedom of speech, and the issue of false information has an urgent need for research. The first part of this article, about the differences between documents and Internet messages, compares the legal significance of Internet messages from the characteristics of the documents, and then understands the behavior of false information from the crime of forging documents and the crime of using forged documents, but the characteristics of the Internet have far-reaching influence beyond the documents, the real situation still needs to be clarified. In the second part, we try to define false information from the classification. According to the content of the message and the behavior of the actor, the classification is divided into disinformation behavior, misinformation behavior and fake news. To compare the protection of freedom of speech in the online world and the physical world, the purpose is to explore the true meaning of freedom on the protection of anonymous speech and the principle of“inviolability of editorial discretion”for news media from the judicial practice in Japan and the United States. The third part discusses whether the current legislative model of dangerous offenses and the effect of control measures will erode the modern democratic rule of law and violate the principle of modest restraint and responsibility of the criminal law. Finally, it is a synthesis of insights on the theme of false information crime, from legislation to self-discipline principles, and puts forward the research experience and suggestions of this article.