The present invention relates to novel urea derivatives and, more particularly, to novel urea derivatives with histone deacetylase (HDAC) inhibitory activity, isomers thereof, pharmaceutically acceptable salts thereof, their use for the preparation of a medicaments comprising the same, a pharmaceutical composition comprising the same, a treatment method using the composition, and a method for preparing novel urea derivatives. The novel urea derivatives as selective histone deacetylase (HDAC) inhibitors are effective for the treatment of histone deacetylase-mediated diseases such as malignant tumors, inflammatory diseases, rheumatoid arthritis, neurodegeneration, etc.