Our perspective of Korean legal system that basically came from the European continental system of laws makes it hard for us to easily access Anglo-American legal theories and system. The issue of this paper involves with the doctrines of mistake in substantive criminal law. It must be meaningful to understand the Anglo-American doctrines of mistake, to clarify our understanding of the doctrines. First of all, for the rules of mistake of fact, the Anglo-American legal tradition takes the same standpoint with ours. In other words, not only for the issue of mistake of an object but also for the issue of mistake of method of action, the Anglo-American criminal law recognizes the criminal responsibility based on intent. Particularly, for the issue of mistake of method of action, there have been no difficulties to resolve the relevant cases based on the principle of transferred intention. Now, the principle is supported by a majority of courts and scholars. For the matter of mistake of law, the Anglo-American tradition of law consistently has held on to the principle of "Ignorantia iuris non excusat(Ignorance of law is not an excuse)." Nonetheless, in the 20th century of the industrial societies that bear complex statutes and regulations, since it cannot be fully assumed that anybody should know about them, many exceptions for the principles have been adopted. This article deals with American Model Penal Code 2.04 through the analysis of the exceptions for the principle of 'Ignorance of law is not a mistake.'