In the 2005 amendment of the General Provisions of the Criminal Code, legislators modified the legal effect of the inevitable prohibition mistake to negate guilt. This amendment is considered to be the fulfill-ment of the guilt principle, and is to be universally endorsed. However, this study points out that the theory is not the best solution to implement the guilt principle. It regards “illegality cognition” as an element inde-pendent of subjective intent, which exposes the perpetrators of prohibi-tion mistake to more unfavorable treatment compared to those perpe-trating mistakes of essential factors. This practice has yet to form a rea-sonable basis. In contrast, the intention theory, which was not adopted by legislators, regards “illegality cognition” as an element of subjective intent, and gives the above-mentioned perpetrators equal treatment. That is the proper starting point. As supporters of the theory of guilt criticize it, it has caused excruciating vulnerability of punishment, and improperly given concessions to both habitual criminals and crimes of conscience. In fact, the accusations are exaggerated. Therefore, this study supports intention theory. Whether it is based on mistakes of fact or law, prohibition mistake both negates the effectiveness of intention, and the act is considered to have been committed negligently. By this position, although intention is still an element of subjective iniquity, the connotation has changed so substantially that it is hard to be consistent with the current law. It still awaits amendment by legislators.