Novel chemical species capable of simultaneously alkylating double-stranded DNA and cleaving the same; methods for alkylating and cleaving DNA by using these species; and anticancer agents with the use of these compounds. Compounds represented by the following general formula (I) which are capable of simultaneously alkylating double-stranded DNA and cleaving the same; a method for alkylating DNA and a method for cleaving double stranded DNA by using these compounds; and medicinal compositions with the use of these compounds: B—L—A(I) wherein B represents a chemical structure capable of recognizing the base sequence of DNA, for example, optionally substituted pyrrole-imidazole polyamide; A represents a chemical structure capable of binding to one base of DNA, for example, the alkylation moiety of duocarmycin A; and L represents a linker capable of binding the chemical structures A and B, for example, vinyl.