PURPOSE: To transform the titled plasma easily in high frequency, by treating a yeast cell with an alkali metal ion and contacting the cell with a deoxyribonucelic acid (DNA) to be included in the presence of a nucleic acid as a carrier.

CONSTITUTION: A yeast cell of Saccharomyces genus, etc., is added to an aqueous solution or buffer solution containing ≥10mM of an alkali metal ion such as an organic acid salt of Na ion, etc., at a cell concentration of 1W15×108cell/ ml and treated at or below room temperature. After or simultaneous to the treatment, 0.1mol of the treated liquid is added with 0.5W5μg of a DNA to be included (e.g. plasmid DNA:YRp7) including replication initiation point of yeast), 2W20μg of a nucleic acid as a carrier (e.g. bovine thymus treated with ultrasonic wave) and, if necessary, 70% polyethylene glycol. The mixture is agitated at about room temperature for 0.5W2hr and subjected to a heat pulse of about 50°C to effect the transformation of the cell.