The purpose of this study was to investigate the time-course of morphological processing using event-related potentials(ERPs) in Sino- Korean prefix derivational word. We conducted a lexical priming decision task comparing time-course of a morphological, a semantic, and an orthographic condition. The behavioral data showed significant positivity priming effect in a morphological and semantic priming condition. The ERP data revealed only significant morphological and semantic priming at N250(200-300ms). Also, a reduction of the N400(300-500ms) in the semantic condition. Also, increase of negativity amplitude of semantic priming in P600(550-750ms) observed. This result shows that the morpheme is mainly influenced by the semantic factor but not the orthographic factor from the onset to offset of the recognition of Sino-Korean prefix derivational word.