In this paper, we discuss issues involved with decisions of Korean FTC and the Supreme Court on the case of Posco’s trade refusal against Hyundai Hysco in 2001. We also present evidences of economic analyses for identifying the relevant geographic market. As for the empirical study, Granger causality test and critical loss analysis using AIDS demand system estimation are employed. The results show that the relevant geographic market for hot coil is not restricted to domestic region, but should include North-Eastern Asian countries. The results suggest the Posoco’s trade refusal case should not be regarded as an abuse of market-dominating position. They lead to the same implication with the Supreme courts’ decision that it should not be regarded as an unfair conduct restraining competition, but suggest the different basis of judgement.