An anti-cancer agent contains a phosphine transition metal complex having a ferrocene skeleton, the complex being represented by general formula (3) below: ##STR00001## (wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 each represent a linear or branched alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, or an aralkyl group; A represents a linear or branched alkyl group, a phenyl group, or a hydrogen atom; M.sub.1 represents a transition metal atom selected from the group consisting of gold, copper, platinum, and silver; and X.sub.1 represents an anion).