Disclosed is a plant having an increased grain size, which contains functional-type sh4 gene. Extensive studies have been made on genes involved in the grain sizes of plants, and it is found that a novel function of increasing the sizes of rice hulls, promoting translocation and, consequently, increasing the sizes of grains can be expressed in a rice plant cultivar ("Nihonbare", "Nikomaru", "Oochikara") by introducing a functional allele of sh4 gene derived from a wild-type rice plant into the rice plant cultivar by transformation.
