Substituted benzylthiazolidine-2,4-dione derivatives capable of, as a ligand of human peroxisome proliferator-activated receptor (PPAR), enhancing the transcriptional activity of the receptor and showing effects of lowering blood sugar level and lowering lipid level; and a process for producing the same. Novel substituted benzamide derivatives represented by general formula (1), pharmaceutically acceptable salts thereof and hydrates of the same wherein A represents optionally substituted phenyl, optionally substituted phenoxy or optionally substituted benzyloxy.