A process for preparing bleomycinic acid having a melting point of 228.degree.-230.degree.C. (decomposition) and an analysis of C : 40.80%, H : 5.29%, N : 16.45%, O : 24.78%, S : 4.53%, Cl : 3.37%, and Cu : 4.78% which is characterized by being soluble in water, difficultly soluble in methanol, acetic acid and dimethylsulfoxide, and insoluble in ethanol, ethyl acetate, acetone and ether, and which tests positive to Pauly and Ehrlich reactions but tests negative to ninhydrin, Sakaguchi, Dragendorf, Tollens, ferric chloride, Fehling and Molish reactions, and which has a maximum ultraviolet absorption spectrum at 246 m.mu. and 292 m.mu. and which has an infrared absorption spectrum bands at 3350, 1720, 1670, 1640, 1580, 1460, 1365, 1050, 770 (cm.sup.-.sup.1), and which can be hydrolyzed to yield 2'-(2-aminoethyl)-2,4'-bithiazole-4-carboxylic acid, L-threonine, 4-amino-3-hydroxy-2-methyl-.eta.-valeric acid, .beta.-hydroxy-histidine, .beta.-amino-.beta.-(4-amino-6-carboxy-5-methylpyrimidine-2-yl)-propionic acid, L-.beta.-amino-alanine, L-gulose and 3-0-carbamoyl-D-mannose, which comprises hydrolyzing bleomycin in the presence of a mycelium mass or enzyme.