The present invention provides a method for improving transformation efficiency of a plant. The method according to the present invention comprises the use of a nucleic acid encoding the amino acid sequence set forth in SEQ ID NO: 2 or 4, or a nucleic acid encoding a polypeptide comprising an amino acid sequence having at least 85% identity with the amino acid sequence set forth in SEQ ID NO: 2 or 4, and having a function of improving transformation efficiency of a plant.