The present invention relates to novel compounds having histone deacetylase 6 (HDAC6) inhibitory activity, stereoisomers thereof or pharmaceutically acceptable salts thereof, the use thereof for the preparation of therapeutic medicaments, pharmaceutical compositions containing the same, a method for treating diseases using the composition, and methods for preparing the novel compounds. The novel compounds, stereoisomers thereof or pharmaceutically acceptable salts thereof according to the present invention have histone deacetylase 6 (HDAC6) inhibitory activity and are effective for the prevention or treatment of HDAC6-mediated diseases, including infectious diseases; neoplasms; endocrine, nutritional and metabolic diseases; mental and behavioral disorders; neurological diseases; diseases of the eye and adnexa; cardiovascular diseases; respiratory diseases; digestive diseases; diseases of the skin and subcutaneous tissue; diseases of the musculoskeletal system and connective tissue; or congenital malformations, deformations and chromosomal abnormalities.