Exceptional Case Marking (ECM henceforth) refers to Case marking of the embedded subject by the matrix verb. The construction in which ECM occurs is called ECM construction. As its name implies, it is exceptional in that two elements in different local domains are involved. This paper aims at answering several questions concerning the ECM construction in Korean: (A) Why is there such a construction as the ECM construction? (B) Does the subject of the complement clause raise to the matrix clause? (C) Why is ECM only available in the /w construction, but not in other constructions? (D) What is the categorial status of the ko construction? I make a proposal that ECM is a syntactic realization of pragmatic force `Focus`. Thus, the complement subject raises into the Spec of the matrix vP to be assigned INT reading as discussed in Chomsky (2001) in OS languages. The movement is possible across the ko construction that is assumed to be a CP because Case assignment via the p(ostpositional) complementizer requires the complement subject to raise into the Spec of CP to meet Spec/Head agreement. Other clausal complements in Korean do not allow ECM since Case transmission is not available and nominal CPs do not allow movement into its Spec.