The present invention relates to novel azaindole derivatives, and more particularly, to novel azaindole derivatives having histone deacetylase (HDAC) inhibitory activity, isomers thereof, pharmaceutically acceptable salts thereof, hydrates thereof or solvates thereof, the use thereof for the preparation of pharmaceutical compositions, pharmaceutical compositions containing the same, a method of treating disease using the pharmaceutical compositions, and methods for preparing the novel azaindole derivatives. The novel azaindole derivatives according to the present invention are selective histone deacetylase (HDAC) inhibitors, and may be used as agents for treating malignant tumor diseases, inflammatory diseases, rheumatoid arthritis, and neurodegenerative diseases.
