Disclosed is a technique which is for duplicating across a wide region any large region on a chromosome of a fungus belonging to Aspergillus strain, and which enables the stable and systematic acquisition of a previously un-acquirable fungus belonging to the Aspergillus strain having novel traits. Disclosed is a transformant wherein a transformation marker gene sequence is arranged on the outside of terminals (5, 3) of a region so as to sandwich an arbitrary region of a chromosome, and chromosome duplication has taken place by means of homologous recombination after double strand breakage generated in a homologous region inside the gene. Also disclosed is a method for duplicating an arbitrary region of a chromosome of a fungus belonging to Aspergillus strain by culturing said transformant.
