PROBLEM TO BE SOLVED: To provide a cultivation method of a sweet potato which can utilize bacterial acting usefully during growth to secure a stable crop yield while a risk of infection with harmful bacteria can be reduced.SOLUTION: In a cultivation method of a sweet potato, a scion B1 collected from a seedling B for the scion and a rootstock A1 collected from a seedling A for the rootstock which is raised in an approximately aseptic condition compared with the seedling B for the scion are grafted. The grafted seedling C consisting of the rootstock A1 and the scion B1 is raised. When the rootstock A1 is collected from the seedling A for the root stock, the collection is performed so that a leaf 5 raised from a vine 6 to be cut or a vine 7 branched off from the vine 6 is left on the rootstock A1 side. The rootstock A1 is collected from the aseptic seedling raised in the aseptic condition.
