In the court case of Jun 29 2017 ruling 2017Do3808, Supreme Court ruled that breaking the duty of returning or discarding trade secrets after resignation by revealing trade secrets to competitors or keeping it for own interest is enough to establish post-resignation professional misappropriation. And Supreme Court decided ruled that one cannot be a subject of professional misappropriation after 1year of resignation unless ‘special consideration’ is needed. Therefore, the accused, who created a program based on company’s particular file, cannot be a subject of additional professional misappropriation since the action of the accused was based on already-established professional misappropriation. Furthermore, the Supreme Court ruled that the accused complicit cannot be a complicit of the professional misappropriation since the action of accused complicit is based on already-established professional misappropriation as well. Therefore, the Supreme Court returned the case to the lower court. Based on this case, there is question regarding the relationship between perpetrated time of professional misappropriation and the status of being in charge of the transaction of others’ business after resignation. There is also a question regarding the level of execution based on the speciality of professional misappropriation. This case study is done based on those questions. Then this case study did the reviewed the relationship between the intention of misappropriation and intention of unlawful gains that needs to be proved in order to establish professional misappropriation crimes. The Supreme Court’s ruling that the accused is a subject of already-established professional misappropriation due to nonperformance of returning or discarding trade secrets is problematic. It is problematic for following reasons: First, it ruled out the possibility of accusing the complicit by deciding the perpetrated time as the period of resignation. Second, it contains the possibility of turning the characteristic of misappropriation from offense provoking specific danger to abstract endangerment offenses.