The present invention relates to: a novel compound having a histone deacetylase 6 (HDAC6) inhibitory activity； an optical isomer thereof or a pharmaceutically acceptable salt thereof； a use thereof for preparing a therapeutic pharmaceutical preparation； a pharmaceutical composition containing the same and a treatment method using the composition； and a preparation method therefor. According to the present invention, the novel compound and the optical isomer thereof or pharmaceutically acceptable salt thereof have histone deacetylase 6 (HDAC6) inhibitory activity and are effective in preventing or treating HDAC6-associated diseases including: infectious diseases； neoplasm； endocrine, nutritional and metabolic diseases； psychological and behavioral disorders； neurological disorders； eye and adnexa diseases； circulatory system diseases； respiratory system diseases； digestive system diseases； skin and subcutaneous tissue diseases； musculo-skeletal system and connective tissue diseases； or congenital malformations, deformations and chromosomal abnormalities.
