Sliding-mode control is known as a popular approach of robust control methods. Fuzzy sliding-mode control method has been commonly used to prevent chattering phenomenon, drastic change of control factor, around sliding surface in sliding-mode control. In Hedge-algebras theory, inherent order relationships among linguistic values of each linguistic variable are always guaranteed and these values are determined by isomorphism mapping called semantically quantifying one based on a few fuzziness parameters of each linguistic variable instead of using fuzzy sets. In this paper, sliding-mode hedge-algebras-based controller is designed and applied in active control of a structure subjected to earthquake in order to show advantages of the proposed method.