Indolopyrrocarbazole derivatives represented by formula (I) and the pharmaceutically acceptable salts thereof have excellent antitumor activity as evidenced by their in vitro proliferation inhibiting activity against mouse leukemia cell, human gastric cancer cell, human lung cancer cell and human colon cancer cell, ##STR1## wherein R.sup.1 and R.sup.2 independently represent, for example, a hydrogen atom or various hydrocarbon groups which may be substituted or heterocyclic groups which may also be substituted; or a group --Y--R.sup.3 where Y represents a carbonyl group, thiocarbonyl group or sulfonyl group and R.sup.3 represents a hydrogen atom or one of various aliphatic, cycloaliphatic, aryl, nitrogen-containing (e.g. amino, hydrazino, etc) or heterocyclic groups, which groups may be substituted by various substituents; or R.sup.1 and R.sup.2 may combine to represent a lower alkylidene group which may be substituted; or R.sup.1 and R.sup.2, together with the N-atom to which they are bonded form a heterocyclic group which may be substituted;G represents a pentose or hexose group; and X.sup.1 and X.sup.2, independently, represent, for example, hydrogen, halogen, amino, hydroxyl, alkoxy, aryloxy, carboxyl, alkoxycarbonyl or alkyl. These compounds have improved water solubility as compared to rebeccamycin.