Provided are a seed-coating agent, coated seeds, and a seed-coating method that, with respect to the coating of seeds with an iron-based powder, improve usability and the strength and hot-water resistance of a coating layer. This seed-coating agent is used to coat the surface of seeds and includes: a polyvinyl-alcohol-resin aqueous solution that is produced by dissolving in water a polyvinyl alcohol resin that is at least 90.0 mol% saponified and has a polymerization degree of no more than 2000； and an iron-based powder that includes iron oxide powder and/or iron powder.本發明提供一種在將鐵系粉體被覆於種子上時改善作業性、被覆層的強度及耐溫水性的種子被覆劑、被覆種子及種子被覆方法。本發明的種子被覆劑用於被覆種子表面，且包含：將皂化度為90.0 mol%以上、聚合度為2000以下的聚乙烯醇系樹脂溶解於水中而成的聚乙烯醇系樹脂水溶液；以及含有氧化鐵粉及/或鐵粉的鐵系粉體。
