The uses of Upper Palaeolithic stone tools and plants at the Nishitaragasako site, Kagoshima, were explored by analysing starch residues on the tools. The total starch granule numbers recorded were 160 from 11 sampled stone tools. The quantities of starch found by point sampling were compared on the working and non-working surfaces of stone slabs and grinding stones. More starch granules were found on working surfaces, and they may have been used for processing plants. But no starch granules on working surfaces may have been used for stone tool making. The co-occurrence of spherical and pentagonal starch granules on individual tools suggests that more than two plant species were utilized within the working life of individual grinding stones. Initial visual comparisons of ancient starch samples and modern reference samples suggested the possible presence of 13 genera and 29 identifiable species. The candidates for ancient presence at the Nishitaragasako site include Castanea crenata, Quercus, Juglans ailanthifolia, Pteridium aquilinum, and Cardiocrinum. These candidates were indicated by the size and geometric form of starch granules.