The criminal lawsuit structure in late Chosun Dynasty before KABO reform did not enable speedy trial, as judicature and administration functions were not separated, and the process was dependent on 'Courtesy' that is the governing principle of Confucianism. Also, as the trial structure mandatorily required confession, trial process and criminal administration process were not separated, and torture and defendant replacement by servants was widely prevalent as problematic. The purpose of this study is to review how these structural problems in lawsuit was handled in KABO reform at late Chosun Dynasty. Especially it would be meaningful to reveal how the traditional inquisitorial lawsuit structure was migrated to accusatorial system in this period. This study reviews the lawsuit structure by differentiating between before and after Court Organization Act with regard to criminal lawsuit structure. Therefore,this study compares criminal lawsuit structure during the period between June 1894(lunar year) and March 1895, against another structure that came in after Court Organization Act promulgated as Law No.1 by the coalition cabinet by KIM Hong Jip and PARK Young Hyo, based on the agenda presented by National Intelligence Office. First of all, the lawsuit structure before Court Organization Act reveals that unification of jurisdiction function that was dispersed between administrative institutions was emphasized, rather than the concept of separation between administration and judicature. However, being basically bound within the inquisitorial lawsuit structure, unification of jurisdiction itself looks as a failure. Thereafter, establishment of law school for improved quality of judge did not come true. Prohibition on torture and limitation on defendant replacement by servants were nothing more than declaratory slogan, within the unchanged situation of requiring confession as mandatory. Especially without overcoming mandatory confession lawsuit structure, trial process and criminal administration process could not be separated This situation continued until November 1906, when Criminal Enforcement Law draft was enacted, stipulating 'trial by evidence doctrine' and 'free belief doctrine'After Court Organization Act, civil and criminal lawsuit was differentiated by Civil & Criminal Lawsuit Regulation. However, by victim's submission of private indictment together with public indictment, parallel structure between civil procedure and criminal procedure was operational. This was rather different from modern civil and criminal lawsuit process. Henceforth this study shows that the victim in criminal procedure had some burden of proof. What is remarkable is that after Court Organization Act, lawsuit structure escaped traditional inquisitorial lawsuit structure and switched to accusatorial system dramatically. At this period, even though prosecutor had status as preliminary judge,accusatorial system can be partially identifiable from the viewpoint of prosecutors'authority to file indictment, independency from judges and human right-protective status. At this period, unification of jurisdiction that was unsuccessful beforehand seems to be achieved by establishment of court. With regard to trial process, modern hearing process seems to become in place. However, it is regrettable that establishment of court was not going well, hence disobedience of regional trial was handled by High Court rather than Circuit Court. Furthermore, as regional courts were delayed in establishment, existing regional legal officer had concurrent position of judge and prosecutor, existing problems remained intact in case of regional lawsuit.