According to the present invention, a gene having a novel function that can cause an increase or decrease in seed protein content is searched for. A chimeric protein obtained by fusing a transcription factor consisting of a protein comprising an amino acid sequence shown in any of the even-numbered SEQ ID NOS: 1 to 76 and a functional peptide capable of converting an arbitrary transcription factor into a transcriptional repressor or a transcription factor consisting of a protein comprising an amino acid sequence shown in any of the even-numbered SEQ ID NOS: 77 to 84 is expressed in a plant.
