PURPOSE: To easily obtain the title endonuclease by transforming a host with recombinant plasmid incorporated with chromosome DNA fragment containing AccI restriction endonuclease gene of specific microorganism origin followed by culturing and then collecting the enzyme produced.

CONSTITUTION: Chromosome DNA fragment containing AccI restriction endonuclease gene of Acinetobacter calcoaceticus origin is incorporated into plasmid, and using the resultant recombinant plasmid, host (e.g. Escherichia coli) is transformed and the resultant host is cultured to produce AccI restriction endonuclease. Thence, the objective AccI restriction endonuclease is collected from the cultured product. Thereby, mass production of the objective AccI restriction endonuclease can be easily accomplished without the need for removing both AccII and AccIII restriction endonucleases because of effecting no production thereof.