This paper argues for the presence of an agreeing functional head in Japanese, on the basis of an ellipsis phenomenon called Sluicing. It is argued that the existence of Sluicing, together with the functional head licensing approach to ellipses, implies that an agreeing Comp exists in Japanese and that the presence of what I call multiple Sluicing evidence one-to-one Spec-Head agreement in the language. This study has implications for the theory of economy, the comparative syntax of English and Japanese, and the issues concerning functional categories and syntacticwh-movement in Japanese.