Korea Fair Trade Commission drastically changed Fair Trade Act, in particular, codes of regulation on unfair collusion in the end of 2004. This study investigates the effect of the regulation change on the formation of cartel, antitrust damage suit, and the imposition of administrative fine. And also, this research explores on the types of abuse in the levy of administrative fine through the deep analysis of the existing judicial precedent cases. This study suggest that the government agency should asses the basic fine on the basis of proper damage estimation, not on the basis of the certain percentage of gross sales. This legal approach may help the consistency, the stability, and predictability of legal enforcement. This study also suggest that at the stage of active antitrust damage suit, the financial remedy rely on damage suit and the fine focus on administrative regulation reflecting dead weight loss and enforcement cost due to the collusion in oligopoly market. The punitive compensation system needs to be introduced restrictively in hard-core cartels. This research also discusses the limit and the irrelevance of coercive investigation right of the agency. Finally, it also propose that the agency delete the code of the unfair collusion inference and adopt the actual inference based on solid circumstantial evidence.