This case study illustrates the privatization process of POSCO which was established as government-owned in 1968 and privatized in 2000, focusing on the process itself and its performance after privatization in relation to the change in governance structure as well as corporate mechanism. Differing from typical Korean corporate governance model in which companies are run by owner managers who are mostly the biggest shareholders, POSCO carries a ‘decentralized ownership- professional manager’ structure. This case study investigates the “hidden and invisible ownership power” under the decentralized ownership of POSCO and its related performance, so that it may further discuss a new desirable corporate governance model in Korea. Particularly, this case study focuses on the decisions about the ownership and management type during the POSCO’s privatization finalized in October 2000, together with the changes of corporate management mechanism and of global steel industrial competitions. And as a consequence it reveals some important factors that should be considered in and out of a government owned enterprise when it is processed to be privatized.