The present invention provides an artificial nuclease comprising a DNA-binding domain and a function domain linked to each other via a polypeptide consisting of 35 to 55 amino acid residues wherein amino acid residues at two sites in a DNA-binding module contained in a DNA-binding domain exhibit a mode of repetition that is different for every four DNA-binding modules; a vector for expressing said artificial nuclease; a vector library for preparing said vector; and a vector set for preparing said vector library.