According to the present invention, a novel mutated plant is provided based on findings obtained by analyzing the function of a functionally unknown gene having a CPC-like Myb sequence. The function of any one of the following proteins is suppressed: (a) a protein comprising the amino acid sequence set forth in SEQ ID NO: 2; and (b) a protein which comprises an amino acid sequence having a substitution, deletion, addition, or insertion of one or more amino acids in the amino acid sequence set forth in SEQ ID NO:2, and is capable of acting as a transcription factor for controlling epidermal cell differentiation. A plant having a characteristic phenotype, for example which can grow to a larger size than the wild-type plant, can be obtained by suppressing the function of the above protein.
