Provided is an anti-cancer agent composition exhibiting excellent solubility and exerting high anti-cancer activity while exhibiting low toxicity. An anti-cancer composition characterized by containing a cyclodextrin compound and a phosphine transition metal complex represented by general formula (1). (In the formula, R1 and R2 represent a linear or branched alkyl group, a cycloalkyl group, a cycloalkyl group having a substituent, an adamantyl group, a phenyl group, or a phenyl group having a substituent, have a carbon number between 1 and 10, and may represent the same group or different groups. R3 and R4 represent a hydrogen atom or a linear or branched alkyl group, have a carbon number between 1 and 6, and may represent the same group or different groups. R3 and R4 may form a saturated or unsaturated ring by bonding to one another and said saturated or unsaturated ring may have a substituent. M represents a transition metal atom selected from among gold, copper, and silver. X- represents an anion.)
