Novel staurosporin derivatives represented by formula (I) (wherein R 1 represents hydrogen, lower alkyl, formyl or amino, R 2 represents hydrogen, formyl, lower alkanoyl or a group formed by removing a hydroxy moiety from the carboxyl group of an a-amino acid whose amino group may optionally be protected, one of X 1 and X 2 represents hydrogen and the other represents hydrogen, hydroxy, lower alkoxy or lower alkylthio, or X' and X 2 are taken together to form oxygen, provided that, when R 1 and R 2 are both hydrogen atoms and one of X 1 and X 2 is hydrogen, the other represents a group other than hydrogen or hydroxy) and their pharmacologically acceptable salts are disclosed. These compounds inhibit protein kinase C and have a cell growth inhibiting activity.