PROBLEM TO BE SOLVED: To provide a seed plug capable of enhancing the germination rate and growing rate of seeds planted in a ground contaminated with heavy metals and thus efficiently and stably purifying contaminated soil, and to provide a method for purifying contaminated soil.SOLUTION: The seed plug is produced by enclosing seeds of a plant with a medium, which is produced by mixing, relative to 65-97% of seed growing object soil including fertilizer or a small amount of nutrient salt, a raw material composed of any one powder of arum root powder, agar powder, starch, powdered arrowroot, corn starch and sticky rice powder or a mixed powder of two or more thereof in the range of 3-35%, with addition of water followed by drying. The method includes: a seed plug production step； a growing step of planting the seed plug in the ground of the soil contaminated with heavy metals to grow the plant； and a recovery step of harvesting roots, leaves, stems and flowers of the plant grown in the growing step followed by drying and incineration, thereby recovering the heavy metals absorbed by the plant.
