According to law No. 5 of 1999 agreement in the forms of cartel was prohibited since a cartel is cooperation of several manufacturers of particular products. Commission for the supervision of business competition (KPPU) was established based on article 30 paragraph 1 of law no. 5 of 1999 on prohibition of monopolistic practices and unfair competition. There were 32 feedloter companies suspected to be the member of corporate cartel on imported beef and they have been investigated by the commission. There were two research questions (1). How does Commission for the Supervision of Business Competition (KPPU) decide the imported beef case as cartel agreement? And (2). What are the mechanism of Commission for the Supervision of Business Competition (KPPU) in resolving the cartel cases of imported beef? The research was conducted under normative empirical method and the data were collected from observation and interview. The results indicated that (1).the detention of supply of imported beef in cartel practice is prohibited from entering into an agreement, with a competing business actor, intending to influence prices by regulating the production and or marketing of goods and service (2). In resolving the cartel case of imported beef, the KPPU had done several stages; indication collection, preliminary examination, advanced examination, judgment adjudication, and execution of decision. It is recommended that businessman should pay more attention to the provisions of law in accordance with the principles of fair business competition and Comission for the Supervision of Bussiness Competition (KPPU) should do a thorough investigation in resolving the case.