To obtain a vector capable o producing a heteroantibody for medicine or the like by transducing damages to a part of an endogenous immunoglobulin by homologous recombination of the sequences having homology with a part of endogenous immunoglobulin gene locus and endogenous immunoglobulin gene locus.

The method inactivates the endogenous immunoglobulin gene locus of mammal of non primates by transducing damages to at least a part of the endogenous immunoglobulin gene locus by replacing at least a part of the endogenous immuonoglobuin gene locus with a marker gene such as neomycin-resistant gene or the like using homologous recombination of the DNA sequence having homology with a part of the endogenous immunoglobulin gene locus and the endogenous immunoglobulin gene locus, and obtaining the subject vector giving cells lacking ability of producing endogenous immunoglobulin and having ability to produce the heteroimmunoglobulin of human or the like by transducing heteroimmunoglobulin gene such as human or the like to genome of the mammal of non primates.