By inhibiting the function of a transcription factor that promotes transcription of a gene associated with the amounts of lignin and cellulose, a plant in which the amounts of lignin and cellulose are reduced without reducing the amount of glucan is produced. In this plant, glucan in the obtained cell wall components is in the state of highly easily undergoing saccharification. In this plant, moreover, natural dehiscence of pods is suppressed. A method of inhibiting the transcription factor includes a method in which a chimeric gene between a transcription factor gene and a polynucleotide that encodes a functional peptide capable of converting the transcription factor into a transcription repressor is introduced into a plant cell so that a chimeric protein in which the transcription factor is fused with the functional peptide is produced in a plant cell, and a method of inhibiting the expression of the transcription factor, such as knockout method or RNAi method. Thus, a plant in which the amounts of lignin and cellulose are reduced without reducing the amount of glucan is provided.