This article is an analysis of administrative criminal law theory. The ‘administrative criminal law theory’, which is unfamiliar to most people and even to some criminal law, scholars was introduced to Korea through Germany and Japan. Even though the theory has disappeared in the birthplace and been ineffective in the gateway, it still takes possession of a part of administrative law text book, and penalty provisions still exist in the existing law of Korea. The purpose of this study is whether the administrative criminal law theory is still valid and fair, and whether the existing law provisions based on the theory is constitutional. In this current study, ‘administrative criminal law’ theory was analyzed both theoretically and practically. Through an examination of administrative procedures as modified criminal procedures and of monetary penalty system, the theory, which is originated from particular militaristic and totalitarian states, early 20th century Germany and Japan, is no longer valid in 21th century Korea and shall not have any necessity to be kept. On the contrary, it is concluded that the theory impairs the unity of the legal order of a country and threats people’s legal life. Furthermore, problems as a law-governed country regarding modified criminal procedures which were made to simplify many criminal cases caused due to excessively legislated penalties are pointed out here, and plans are groped to solve those problems. A re-establishment is required through more thorough legislative studies and theoretical examination under the unity of nation’s legal order and the prediction possibility of people’s legal life, and at the same time under the prospect about establishing the system of punishment law for effective enforcement of nation operation.