Sino-Japanese floristic region, including the flora of Japan, has high plant diversity. Primary focus of my research is to understand how plants diversified and evolved in the region. To achieve it, I have conducted researches based on field works, morphological observation, and molecular analyses from the viewpoint of different geographical scale and different evolutionary status. Especially, I focus on endemic plant groups in the region (Aucuba, Helwingia, Pertya, etc.), plant groups diversified in the region (Aristolochia, Arisaema, etc.), and endemic plants in the Ogasawara Islands.