The present invention relates to geldanamycin derivatives, benzoquinone ansamycin biosynthesized by gene manipulation of Streptomyces hygroscopicus subsp. duamyceticus and the method producing them, more particularly to a geldanamycin O-carbamoyl transferase gene(gel8)-inactive mutant, the method producing it and geldanamycin derivatives, 4,5-dihydro-7-O-descarbamoyl-7-hydroxy geldanamycin and 4,5-dihydro-7-O-descarbamoyl-7-hydroxy-17-O-demethyl geldanamycin. Since geldanamycin derivatives of the present invention suppress Hsp90 like geldanamycin, they can effectively be used for antibiotic, antifungal, antiviral, anti-inflammatory and antitumor agents and an immune suppressant.